Set build date using the Go linker

build.sh

#!/bin/bash

go build -ldflags "-X main.buildDate `date -u +%Y-%m-%d.%H%M%S`"

main.go

package main

import "fmt"

var buildDate string

func main() {
	fmt.Println(buildDate)
}

The Go linker has the command line option -X used to set the value of an otherwise uninitialized string variable.