move the variables set during the building process into the core package

pkg/core/application.go

@@ -1,4 +1,21 @@
 package core
 
+import "fmt"
+
 // ApplicationName represents the application name
 const ApplicationName = "ezBookkeeping"
+
+// Version, CommitHash and BuildTime are set at build
+var (
+	Version    string
+	CommitHash string
+	BuildTime  string
+)
+
+func GetOutgoingUserAgent() string {
+	if Version == "" {
+		return ApplicationName
+	}
+
+	return fmt.Sprintf("%s/%s", ApplicationName, Version)
+}