Several changes

Switch timerlist to a slice of pointers to timers
Go mod

timer.go

@@ -88,7 +88,9 @@ func NewTimer() *Timer {
 // ParseTimer parses the input text string into a Timer struct
 func ParseTimer(text string) (*Timer, error) {
 	var err error
-	timer := Timer{}
+	timer := Timer{
+		AdditionalTags: make(map[string]string),
+	}
 	timer.Original = strings.Trim(text, "\t\n\r ")
 	originalParts := strings.Fields(timer.Original)
 
@@ -209,3 +211,12 @@ func (timer *Timer) HasProject(project string) bool {
 	}
 	return false
 }
+
+func (timer *Timer) HasTag(name string) bool {
+	_, ok := timer.AdditionalTags[name]
+	return ok
+}
+
+func (timer *Timer) GetTag(name string) string {
+	return timer.AdditionalTags[name]
+}