Add coumentation to errors

contenttype.go

@@ -8,13 +8,20 @@ import (
 )
 
 var (
-	ErrInvalidMediaType          = errors.New("Invalid media type")
-	ErrInvalidMediaRange         = errors.New("Invalid media range")
-	ErrInvalidParameter          = errors.New("Invalid parameter")
+	// Media type in the Content-Type or Accept header is syntactically invalid.
+	ErrInvalidMediaType = errors.New("Invalid media type")
+	// Range of media types in the Content-Type or Accept header is syntactically invalid.
+	ErrInvalidMediaRange = errors.New("Invalid media range")
+	// Media type parameter in the Content-Type or Accept header is syntactically invalid.
+	ErrInvalidParameter = errors.New("Invalid parameter")
+	// Media type extension parameter in the Content-Type or Accept header is syntactically invalid.
 	ErrInvalidExtensionParameter = errors.New("Invalid extension parameter")
-	ErrNoAcceptableTypeFound     = errors.New("No acceptable type found")
-	ErrNoAvailableTypeGiven      = errors.New("No available type given")
-	ErrInvalidWeight             = errors.New("Invalid wieght")
+	// Accept header contains only media types that are not in the acceptable media type list.
+	ErrNoAcceptableTypeFound = errors.New("No acceptable type found")
+	// Acceptbale media type list is empty.
+	ErrNoAvailableTypeGiven = errors.New("No available type given")
+	// Media type weight in the Accept header is syntactically invalid.
+	ErrInvalidWeight = errors.New("Invalid wieght")
 )
 
 // A map for media type parameters.