Rewrite shell signal handling

pkg/shell/shell.go

@@ -1,7 +1,11 @@
 package shell
 
 import (
+	"os"
+	"os/signal"
+	"regexp"
 	"strings"
+	"syscall"
 )
 
 func QuoteSplit(s string) []string {
@@ -39,3 +43,34 @@ func QuoteSplit(s string) []string {
 	}
 	return a
 }
+
+func ReplaceEnvVars(text string) string {
+	re := regexp.MustCompile(`\${([^}{]+)}`)
+	return re.ReplaceAllStringFunc(text, func(match string) string {
+		key := match[2 : len(match)-1]
+
+		var def string
+		var dok bool
+
+		if i := strings.IndexByte(key, ':'); i > 0 {
+			key, def = key[:i], key[i+1:]
+			dok = true
+		}
+
+		if value, vok := os.LookupEnv(key); vok {
+			return value
+		}
+
+		if dok {
+			return def
+		}
+
+		return match
+	})
+}
+
+func RunUntilSignal() {
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
+	println("exit with signal:", (<-sigs).String())
+}