added DieIf/PrintfIf to help with errors

errors/logandstuff.go

@@ -0,0 +1,35 @@
+package errors
+
+import (
+	"fmt"
+	"os"
+)
+
+// DieIf prints msg + err to stderr then exits the program with status code 1
+// it's like a panic, without the stacktrace.
+// use %v in message to print the error, default is "error: %v"
+func DieIf(err error, msg string) {
+	if err != nil {
+		if len(msg) == 0 {
+			msg = "error: %v"
+		}
+		fmt.Fprintf(os.Stderr, msg+"\n", err)
+		os.Exit(1)
+	}
+}
+
+// PrintfIf calls fn (log.Printf or fmt.Printf for example) with msg and err
+// if err != nil, it will return true and call fn(msg, err)
+// example:
+//	if PrintfIf(err, "error: %v\n", log.Printf) {
+//		return
+//	}
+func PrintfIf(err error, msg string, fn func(format string, args ...interface{})) (b bool) {
+	if b = err != nil; b {
+		if len(msg) == 0 {
+			msg = "error: %v"
+		}
+		fn(msg, err)
+	}
+	return
+}