supporting env var for config.toml hostname

config/config.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net"
+	"os"
 	"path"
 	"strings"
 	"time"
@@ -12,6 +13,11 @@ import (
 	"github.com/toolkits/pkg/file"
 )
 
+var envVarEscaper = strings.NewReplacer(
+	`"`, `\"`,
+	`\`, `\\`,
+)
+
 type Global struct {
 	PrintConfigs bool              `toml:"print_configs"`
 	Hostname     string            `toml:"hostname"`
@@ -108,10 +114,16 @@ func (c *ConfigType) GetHostname() string {
 
 	ret = strings.Replace(ret, "$hostname", name, -1)
 	ret = strings.Replace(ret, "$ip", c.Global.IP, -1)
+	ret = os.Expand(ret, getEnv)
 
 	return ret
 }
 
+func getEnv(key string) string {
+	v := os.Getenv(key)
+	return envVarEscaper.Replace(v)
+}
+
 func GetInterval() time.Duration {
 	if Config.Global.Interval <= 0 {
 		return time.Second * 15