Display usage information on error.

error.go

@@ -0,0 +1,12 @@
+package kong
+
+// ParseError is the error type returned by Kong.Parse().
+//
+// It contains the parse Context that triggered the error.
+type ParseError struct {
+	error
+	Context *Context
+}
+
+// Cause returns the original cause of the error.
+func (p *ParseError) Cause() error { return p.error }