feat: implement caldav search

vendor/github.com/dolanor/caldav-go/utils/error.go

@@ -0,0 +1,37 @@
+package utils
+
+import (
+	"fmt"
+	"reflect"
+	"runtime"
+)
+
+type Error struct {
+	method  interface{}
+	message string
+	context interface{}
+	cause   error
+}
+
+func NewError(method interface{}, message string, context interface{}, cause error) *Error {
+	e := new(Error)
+	e.method = method
+	e.message = message
+	e.context = context
+	e.cause = cause
+	return e
+}
+
+func (e *Error) Error() string {
+	pc := reflect.ValueOf(e.method).Pointer()
+	fn := runtime.FuncForPC(pc).Name()
+	msg := fmt.Sprintf("error: %s\nfunc: %s", e.message, fn)
+	if e.context != nil {
+		tname := reflect.ValueOf(e.context).Type()
+		msg = fmt.Sprintf("%s\ncontext: %s", msg, tname.String())
+	}
+	if e.cause != nil {
+		msg = fmt.Sprintf("%s\ncause: %s", msg, e.cause.Error())
+	}
+	return msg
+}