C-style conditional compilation in golang

Does golang support

#define DEBUG 

#ifdef DEBUG 
  fmt.Println("Debug message..."); 
#endif 

So I can build a debug version with zero runtime overhead?

Go does not have a preprocessor or a macro system. What you could do is pass in tags to go build through the -tags flag and use build constraints. To do this you would need two versions of the same source and only one would get build depending if the tag is present or not.

Look at build constraints in https://golang.org/pkg/go/build/

main_debug.go

// +build debug

package main

import (
    "fmt"
)

func main() {
    fmt.Println("Debug build")
}

main_release.go

// +build !debug

package main

import (
    "fmt"
)

func main() {
    fmt.Println("Release build")
}

Here go build would compile with main_release.go and go build -tags debug would compile with main_debug.go