Printing output to a command window when golang application is compiled with -ldflags -H=windowsgui

Question

I have an application that usually runs silent in the background, so I compile it with

go build -ldflags -H=windowsgui 

To check

Answer 1

Answer above was helpful but alas it did not work for me out of the box. After some additional research I came to this code:

// go build -ldflags -H=windowsgui
package main

import "fmt"
import "os"
import "syscall"

func main() {
    modkernel32 := syscall.NewLazyDLL("kernel32.dll")
    procAllocConsole := modkernel32.NewProc("AllocConsole")
    r0, r1, err0 := syscall.Syscall(procAllocConsole.Addr(), 0, 0, 0, 0)
    if r0 == 0 { // Allocation failed, probably process already has a console
        fmt.Printf("Could not allocate console: %s. Check build flags..", err0)
        os.Exit(1)
    }
    hout, err1 := syscall.GetStdHandle(syscall.STD_OUTPUT_HANDLE)
    hin, err2 := syscall.GetStdHandle(syscall.STD_INPUT_HANDLE)
    if err1 != nil || err2 != nil { // nowhere to print the error
        os.Exit(2)
    }
    os.Stdout = os.NewFile(uintptr(hout), "/dev/stdout")
    os.Stdin = os.NewFile(uintptr(hin), "/dev/stdin")
    fmt.Printf("Hello!\nResult of console allocation: ")
    fmt.Printf("r0=%d,r1=%d,err=%s\nFor Goodbye press Enter..", r0, r1, err0)
    var s string
    fmt.Scanln(&s)
    os.Exit(0)
}

The key point: after allocating/attaching the console, there is need to get stdout handle, open file using this handle and assign it to os.Stdout variable. If you need stdin you have to repeat the same for stdin.