Fair timeout; Better errors handling

errors.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+type imgproxyError struct {
+	StatusCode    int
+	Message       string
+	PublicMessage string
+}
+
+func (e imgproxyError) Error() string {
+	return e.Message
+}
+
+func newError(status int, msg string, pub string) imgproxyError {
+	return imgproxyError{status, msg, pub}
+}
+
+func newUnexpectedError(err error, skip int) imgproxyError {
+	msg := fmt.Sprintf("Unexpected error: %s\n%s", err, stacktrace(skip+1))
+	return imgproxyError{500, msg, "Internal error"}
+}
+
+var (
+	invalidSecretErr = newError(403, "Invalid secret", "Forbidden")
+)
+
+func stacktrace(skip int) string {
+	callers := make([]uintptr, 10)
+	n := runtime.Callers(skip+1, callers)
+
+	lines := make([]string, n)
+	for i, pc := range callers[:n] {
+		f := runtime.FuncForPC(pc)
+		file, line := f.FileLine(pc)
+		lines[i] = fmt.Sprintf("%s:%d %s", file, line, f.Name())
+	}
+
+	return strings.Join(lines, "\n")
+}