A closer look at the chat's mumblings
Disclaimer: I don't know Go.

Error handling

The sendRequest method may fail,
returning nil,
but the caller in main continues happily as if nothing happened.
In fact, looking at the context of the call in main,
my first impression was that sendRequest magically always succeeds,
which is not the case, and so a bit misleading.

Likewise, parseJson may also fail,
parsing nothing,
but from where you call it,
this is not obvious, which is again a bit misleading.

Naming

It seems [the common convention][1] is to use camelCase or PascalCase for names,
no underscores.
So I suggest to rename the fields of the ChatEvent struct.
I'd go as far as to say use PascalCase for types and camelCase for variables, but this is not so clear in the docs.

The variable parsedJson says nothing about what kind of object it is.
So I'd rename it to chatEvents.

Exceptional users

The list of such users would be better in a global set:


if currentMessage.User_id == -263 || currentMessage.User_id == 125580 {
    // Ignore Captain Obvious &amp; Duga
    continue
}



Too wide lines

The line-end comments in the constant definitions make me scroll to the far right to read them.
Even worse,
while reading the code further down,
when I see lines that seem to end near the right end of the text,
the presence of the horizontal scrollbar makes me wonder if there's something more if I scroll right.
And usually there's nothing, as expected, but this is really annoying.
Please avoid line-end comments if they make the line wider than the longest real line of code.
Or better yet, avoid line-end comments if they will make the line exceed 70 characters.