text: #pragma once
  
  extern "C" {
  #include <nginx.h>
  #include <ngx_config.h>
  #include <ngx_core.h>
  #include <ngx_http.h>
  }
  
  namespace ngx_opentracing {
  //------------------------------------------------------------------------------
  // discover_span_context_keys
  //------------------------------------------------------------------------------
  ngx_array_t* discover_span_context_keys(ngx_pool_t* pool, ngx_log_t* log,
                                          const char* tracing_library,
                                          const char* tracer_config_file);
  }  // namespace ngx_opentracing
  