I'm no windows/386 tip.

C:\go\path\mine\src\a>type main.go
package main

import "fmt"

func main() {
        fmt.Println("Hello")
}
C:\go\path\mine\src\a>go build main.go

C:\go\path\mine\src\a>gdb main.exe
GNU gdb (GDB) 7.2
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>;
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "mingw32".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>;...
Reading symbols from C:\go\path\mine\src\a/main.exe...done.
(gdb) br 'runtime.stdcall'
Breakpoint 1 at 0x40c730
(gdb) r
Starting program: C:\go\path\mine\src\a/main.exe
[New Thread 5524.0x81c]

Breakpoint 1, 0x0040c730 in runtime.stdcall ()
    at C:/go/root/src/pkg/runtime/compiler.go:1
1       // Copyright 2012 The Go Authors.  All rights reserved.
(gdb) l
1       // Copyright 2012 The Go Authors.  All rights reserved.
2       // Use of this source code is governed by a BSD-style
3       // license that can be found in the LICENSE file.
4
5       package runtime
6
7       // Compiler is the name of the compiler toolchain that built the
8       // running binary.  Known toolchains are:
9       //
10      //      gc      The 5g/6g/8g compiler suite at code.google.com/p/go.
(gdb)