Go requires adding a comma after the last argument in the function under certain formatting conditions

[denisvmedia]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.8.1 windows/amd64

What operating system and processor architecture are you using (go env)?

set GOARCH=amd64
set GOBIN=
set GOEXE=.exe
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=C:\Users\user\go
set GORACE=
set GOROOT=c:\tools\go
set GOTOOLDIR=c:\tools\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set CC=gcc
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0
set CXX=g++
set CGO_ENABLED=1
set PKG_CONFIG=pkg-config
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2

What did you do?

Trying to compile this piece of code:

    // func (r *Room) wrapRoomEventHandler(callback EventCallback) EventCallback

    eventHandler := world.getRoom("room").wrapRoomEventHandler(
        func(player *Player, context interface{}, args ...string) (result interface{}) {
            if args[0] == "backpack" && player.inventory == nil {
                    player.inventory = &Inventory{}
                    return "wearing the backpack"
            }
            return context
        } // here it wants me a comma, but why?
    )

What did you expect to see?

This code to be compiled.

What did you see instead?

.\main.go:71: syntax error: unexpected semicolon or newline, expecting comma or )

Actually, it forces me to put a comma after the last closing curly brace. And it is totally understandable for any kind of lists/arrays/slices/etc, but why does it force me to add a comma after the function function argument? (which is the last and the only one)

P.S. Sorry, I'm totally new to go, and probably this is a well-known feature of the language, that I'm not aware of.

[griesemer]

This is working as intended and a well-known syntax aspect of Go.

Because of golang.org/ref/spec#Semicolons, without a comma, a semicolon is automatically inserted, which leads to an incorrect parameter list.

Because of golang.org/ref/spec#Parameters, it's ok to add a comma at the end of a parameter list. Adding the comma has the side-effect of disabling automatic semicolon insertion which makes this work.