Load environment variables from file into program

loadenv.go

package main

import (
	"fmt"
	"os"
	"os/exec"
	"strings"
)

// Source loads variables defined in the path into the current environment
func Source(path string, variables ...string) error {
	sb := strings.Builder{}
	m := make(map[string]bool,  len(variables))
	for _, s := range variables {
		sb.WriteString(fmt.Sprintf("export %s=$%s; ", s, s))
		m[s] = true
	}
	cmd := exec.Command("sh", "-c", fmt.Sprintf("source %s && %s env", path, sb.String()))
	out, err := cmd.Output()
	if err != nil {
		return err
	}
	for _, s := range strings.Split(string(out), "\n") {
		kv := strings.SplitN(s, "=", 2)
		if len(kv) == 2 && m[kv[0]] {
			os.Setenv(kv[0], kv[1])
		}
	}
	return nil
}