<p dir="auto">Received this error. For some additional info, I am only using the <code class="notranslate">std/path</code> module and some function from the <code class="notranslate">Deno</code> global.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="thread 'main' panicked at 'already borrowed: BorrowMutError', /rustc/4fb7144ed159f94491249e86d5bbd033b5d60550/src/libcore/cell.rs:878:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: &lt;std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display&gt;::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1063
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1426
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:204
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:224
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:470
  11: rust_begin_unwind
             at src/libstd/panicking.rs:378
  12: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  13: core::option::expect_none_failed
             at src/libcore/option.rs:1211
  14: deno_core::bindings::send
  15: &lt;extern &quot;C&quot; fn(A0) .&gt; R as rusty_v8::support::CFnFrom&lt;F&gt;&gt;::mapping::c_fn
  16: _ZN2v88internal25FunctionCallbackArguments4CallENS0_15CallHandlerInfoE
  17: _ZN2v88internal12_GLOBAL__N_119HandleApiCallHelperILb0EEENS0_11MaybeHandleINS0_6ObjectEEEPNS0_7IsolateENS0_6HandleINS0_10HeapObjectEEESA_NS8_INS0_20FunctionTemplateInfoEEENS8_IS4_EENS0_16BuiltinArgumentsE
  18: _ZN2v88internalL26Builtin_Impl_HandleApiCallENS0_16BuiltinArgumentsEPNS0_7IsolateE
  19: Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_BuiltinExit
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
fatal runtime error: failed to initiate panic, error 5
Aborted"><pre class="notranslate"><code class="notranslate">thread 'main' panicked at 'already borrowed: BorrowMutError', /rustc/4fb7144ed159f94491249e86d5bbd033b5d60550/src/libcore/cell.rs:878:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.44/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: &lt;std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display&gt;::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1063
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1426
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:204
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:224
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:470
  11: rust_begin_unwind
             at src/libstd/panicking.rs:378
  12: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  13: core::option::expect_none_failed
             at src/libcore/option.rs:1211
  14: deno_core::bindings::send
  15: &lt;extern "C" fn(A0) .&gt; R as rusty_v8::support::CFnFrom&lt;F&gt;&gt;::mapping::c_fn
  16: _ZN2v88internal25FunctionCallbackArguments4CallENS0_15CallHandlerInfoE
  17: _ZN2v88internal12_GLOBAL__N_119HandleApiCallHelperILb0EEENS0_11MaybeHandleINS0_6ObjectEEEPNS0_7IsolateENS0_6HandleINS0_10HeapObjectEEESA_NS8_INS0_20FunctionTemplateInfoEEENS8_IS4_EENS0_16BuiltinArgumentsE
  18: _ZN2v88internalL26Builtin_Impl_HandleApiCallENS0_16BuiltinArgumentsEPNS0_7IsolateE
  19: Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_BuiltinExit
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
fatal runtime error: failed to initiate panic, error 5
Aborted
</code></pre></div>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="C:\workspace&gt;deno-1.0.3.exe
Deno 1.0.3
exit using ctrl+d or close()
&gt; crypto.getRandomValues(new Uint8Array(10))
Uint8Array(10) [
  255, 146, 102,  81,
  25, 238, 144, 127,
  185, 250
]
&gt; "><pre class="notranslate"><code class="notranslate">C:\workspace&gt;deno-1.0.3.exe
Deno 1.0.3
exit using ctrl+d or close()
&gt; crypto.getRandomValues(new Uint8Array(10))
Uint8Array(10) [
  255, 146, 102,  81,
  25, 238, 144, 127,
  185, 250
]
&gt; 
</code></pre></div>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="C:\workspace\deno&gt;deno
Deno 1.0.4
exit using ctrl+d or close()
&gt; crypto.getRandomValues(new Uint8Array(10))
thread 'main' panicked at 'already borrowed: BorrowMutError', /rustc/4fb7144ed159f94491249e86d5bbd033b5d60550\src\libcore\cell.rs:878:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

C:\workspace\deno&gt;"><pre class="notranslate"><code class="notranslate">C:\workspace\deno&gt;deno
Deno 1.0.4
exit using ctrl+d or close()
&gt; crypto.getRandomValues(new Uint8Array(10))
thread 'main' panicked at 'already borrowed: BorrowMutError', /rustc/4fb7144ed159f94491249e86d5bbd033b5d60550\src\libcore\cell.rs:878:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

C:\workspace\deno&gt;
</code></pre></div>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="C:\workspace\deno&gt;set RUST_BACKTRACE=full&amp; deno
Deno 1.0.4
exit using ctrl+d or close()
&gt; crypto.getRandomValues(new Uint8Array(10))
thread 'main' panicked at 'already borrowed: BorrowMutError', /rustc/4fb7144ed159f94491249e86d5bbd033b5d60550\src\libcore\cell.rs:878:9
stack backtrace:
   0:     0x7ff7eaab92df - CrashForExceptionInNonABICompliantCodeRange
   1:     0x7ff7eaada82b - CrashForExceptionInNonABICompliantCodeRange
   2:     0x7ff7eaaaf09c - CrashForExceptionInNonABICompliantCodeRange
   3:     0x7ff7eaabc96c - CrashForExceptionInNonABICompliantCodeRange
   4:     0x7ff7eaabc5bf - CrashForExceptionInNonABICompliantCodeRange
   5:     0x7ff7eaabd147 - CrashForExceptionInNonABICompliantCodeRange
   6:     0x7ff7eaabcccf - CrashForExceptionInNonABICompliantCodeRange
   7:     0x7ff7eaad9130 - CrashForExceptionInNonABICompliantCodeRange
   8:     0x7ff7eaad8f83 - CrashForExceptionInNonABICompliantCodeRange
   9:     0x7ff7e9fdd070 - &lt;unknown&gt;
  10:     0x7ff7e9fcf8ab - &lt;unknown&gt;
  11:     0x7ff7ea4731bb - CrashForExceptionInNonABICompliantCodeRange
  12:     0x7ff7ea4725f8 - CrashForExceptionInNonABICompliantCodeRange
  13:     0x7ff7ea471b46 - CrashForExceptionInNonABICompliantCodeRange
  14:     0x7ff7ea471767 - CrashForExceptionInNonABICompliantCodeRange
  15:     0x7ff7ea2842fc - CrashForExceptionInNonABICompliantCodeRange
  16:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  17:     0x7ff7ea20ff1f - CrashForExceptionInNonABICompliantCodeRange
  18:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  19:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  20:     0x7ff7ea21421e - CrashForExceptionInNonABICompliantCodeRange
  21:     0x7ff7ea213e0c - CrashForExceptionInNonABICompliantCodeRange
  22:     0x7ff7ea0d57a7 - &lt;unknown&gt;
  23:     0x7ff7ea0d4b2a - &lt;unknown&gt;
  24:     0x7ff7ea003be3 - &lt;unknown&gt;
  25:     0x7ff7e9ffb6a1 - &lt;unknown&gt;
  26:     0x7ff7e9fdde9d - &lt;unknown&gt;
  27:     0x7ff7e9fcf71b - &lt;unknown&gt;
  28:     0x7ff7ea4731bb - CrashForExceptionInNonABICompliantCodeRange
  29:     0x7ff7ea4725f8 - CrashForExceptionInNonABICompliantCodeRange
  30:     0x7ff7ea471b46 - CrashForExceptionInNonABICompliantCodeRange
  31:     0x7ff7ea471767 - CrashForExceptionInNonABICompliantCodeRange
  32:     0x7ff7ea2842fc - CrashForExceptionInNonABICompliantCodeRange
  33:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  34:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  35:     0x7ff7ea245a51 - CrashForExceptionInNonABICompliantCodeRange
  36:     0x7ff7ea2c930f - CrashForExceptionInNonABICompliantCodeRange
  37:     0x7ff7ea237dad - CrashForExceptionInNonABICompliantCodeRange
  38:     0x7ff7ea21410c - CrashForExceptionInNonABICompliantCodeRange
  39:     0x7ff7ea0d56de - &lt;unknown&gt;
  40:     0x7ff7ea0d5dac - &lt;unknown&gt;
  41:     0x7ff7ea0d5eaf - &lt;unknown&gt;
  42:     0x7ff7ea199b28 - CrashForExceptionInNonABICompliantCodeRange
  43:     0x7ff7ea199905 - CrashForExceptionInNonABICompliantCodeRange
  44:     0x7ff7ea035ae1 - &lt;unknown&gt;
  45:     0x7ff7ea010321 - &lt;unknown&gt;
  46:     0x7ff7e9ffb436 - &lt;unknown&gt;
  47:     0x7ff7e9fb9380 - &lt;unknown&gt;
  48:     0x7ff7e9fb7ce0 - &lt;unknown&gt;
  49:     0x7ff7e9fc3179 - &lt;unknown&gt;
  50:     0x7ff7e98121fa - &lt;unknown&gt;
  51:     0x7ff7e96f250e - &lt;unknown&gt;
  52:     0x7ff7e9787669 - &lt;unknown&gt;
  53:     0x7ff7e9741a54 - &lt;unknown&gt;
  54:     0x7ff7e98c16f5 - &lt;unknown&gt;
  55:     0x7ff7e9764f20 - &lt;unknown&gt;
  56:     0x7ff7e9948d26 - &lt;unknown&gt;
  57:     0x7ff7eaabcb67 - CrashForExceptionInNonABICompliantCodeRange
  58:     0x7ff7eaacab92 - CrashForExceptionInNonABICompliantCodeRange
  59:     0x7ff7eaabd388 - CrashForExceptionInNonABICompliantCodeRange
  60:     0x7ff7e9768da7 - &lt;unknown&gt;
  61:     0x7ff7eaaeaf44 - CrashForExceptionInNonABICompliantCodeRange
  62:     0x7ffd92e77bd4 - BaseThreadInitThunk
  63:     0x7ffd9398ce51 - RtlUserThreadStart

C:\workspace\deno&gt;"><pre class="notranslate"><code class="notranslate">C:\workspace\deno&gt;set RUST_BACKTRACE=full&amp; deno
Deno 1.0.4
exit using ctrl+d or close()
&gt; crypto.getRandomValues(new Uint8Array(10))
thread 'main' panicked at 'already borrowed: BorrowMutError', /rustc/4fb7144ed159f94491249e86d5bbd033b5d60550\src\libcore\cell.rs:878:9
stack backtrace:
   0:     0x7ff7eaab92df - CrashForExceptionInNonABICompliantCodeRange
   1:     0x7ff7eaada82b - CrashForExceptionInNonABICompliantCodeRange
   2:     0x7ff7eaaaf09c - CrashForExceptionInNonABICompliantCodeRange
   3:     0x7ff7eaabc96c - CrashForExceptionInNonABICompliantCodeRange
   4:     0x7ff7eaabc5bf - CrashForExceptionInNonABICompliantCodeRange
   5:     0x7ff7eaabd147 - CrashForExceptionInNonABICompliantCodeRange
   6:     0x7ff7eaabcccf - CrashForExceptionInNonABICompliantCodeRange
   7:     0x7ff7eaad9130 - CrashForExceptionInNonABICompliantCodeRange
   8:     0x7ff7eaad8f83 - CrashForExceptionInNonABICompliantCodeRange
   9:     0x7ff7e9fdd070 - &lt;unknown&gt;
  10:     0x7ff7e9fcf8ab - &lt;unknown&gt;
  11:     0x7ff7ea4731bb - CrashForExceptionInNonABICompliantCodeRange
  12:     0x7ff7ea4725f8 - CrashForExceptionInNonABICompliantCodeRange
  13:     0x7ff7ea471b46 - CrashForExceptionInNonABICompliantCodeRange
  14:     0x7ff7ea471767 - CrashForExceptionInNonABICompliantCodeRange
  15:     0x7ff7ea2842fc - CrashForExceptionInNonABICompliantCodeRange
  16:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  17:     0x7ff7ea20ff1f - CrashForExceptionInNonABICompliantCodeRange
  18:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  19:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  20:     0x7ff7ea21421e - CrashForExceptionInNonABICompliantCodeRange
  21:     0x7ff7ea213e0c - CrashForExceptionInNonABICompliantCodeRange
  22:     0x7ff7ea0d57a7 - &lt;unknown&gt;
  23:     0x7ff7ea0d4b2a - &lt;unknown&gt;
  24:     0x7ff7ea003be3 - &lt;unknown&gt;
  25:     0x7ff7e9ffb6a1 - &lt;unknown&gt;
  26:     0x7ff7e9fdde9d - &lt;unknown&gt;
  27:     0x7ff7e9fcf71b - &lt;unknown&gt;
  28:     0x7ff7ea4731bb - CrashForExceptionInNonABICompliantCodeRange
  29:     0x7ff7ea4725f8 - CrashForExceptionInNonABICompliantCodeRange
  30:     0x7ff7ea471b46 - CrashForExceptionInNonABICompliantCodeRange
  31:     0x7ff7ea471767 - CrashForExceptionInNonABICompliantCodeRange
  32:     0x7ff7ea2842fc - CrashForExceptionInNonABICompliantCodeRange
  33:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  34:     0x7ff7ea216755 - CrashForExceptionInNonABICompliantCodeRange
  35:     0x7ff7ea245a51 - CrashForExceptionInNonABICompliantCodeRange
  36:     0x7ff7ea2c930f - CrashForExceptionInNonABICompliantCodeRange
  37:     0x7ff7ea237dad - CrashForExceptionInNonABICompliantCodeRange
  38:     0x7ff7ea21410c - CrashForExceptionInNonABICompliantCodeRange
  39:     0x7ff7ea0d56de - &lt;unknown&gt;
  40:     0x7ff7ea0d5dac - &lt;unknown&gt;
  41:     0x7ff7ea0d5eaf - &lt;unknown&gt;
  42:     0x7ff7ea199b28 - CrashForExceptionInNonABICompliantCodeRange
  43:     0x7ff7ea199905 - CrashForExceptionInNonABICompliantCodeRange
  44:     0x7ff7ea035ae1 - &lt;unknown&gt;
  45:     0x7ff7ea010321 - &lt;unknown&gt;
  46:     0x7ff7e9ffb436 - &lt;unknown&gt;
  47:     0x7ff7e9fb9380 - &lt;unknown&gt;
  48:     0x7ff7e9fb7ce0 - &lt;unknown&gt;
  49:     0x7ff7e9fc3179 - &lt;unknown&gt;
  50:     0x7ff7e98121fa - &lt;unknown&gt;
  51:     0x7ff7e96f250e - &lt;unknown&gt;
  52:     0x7ff7e9787669 - &lt;unknown&gt;
  53:     0x7ff7e9741a54 - &lt;unknown&gt;
  54:     0x7ff7e98c16f5 - &lt;unknown&gt;
  55:     0x7ff7e9764f20 - &lt;unknown&gt;
  56:     0x7ff7e9948d26 - &lt;unknown&gt;
  57:     0x7ff7eaabcb67 - CrashForExceptionInNonABICompliantCodeRange
  58:     0x7ff7eaacab92 - CrashForExceptionInNonABICompliantCodeRange
  59:     0x7ff7eaabd388 - CrashForExceptionInNonABICompliantCodeRange
  60:     0x7ff7e9768da7 - &lt;unknown&gt;
  61:     0x7ff7eaaeaf44 - CrashForExceptionInNonABICompliantCodeRange
  62:     0x7ffd92e77bd4 - BaseThreadInitThunk
  63:     0x7ffd9398ce51 - RtlUserThreadStart

C:\workspace\deno&gt;
</code></pre></div>