Deprecation notices in Go

In Go, for a long time, we didn't have a convention to label the deprecated APIs. In the past years, there is new convention emerged to add deprecation notices to the docs.

Today, standard library uses this specific format.

As an example, Go 1.8 deprecates sql/driver.Execer and adds a deprecation notice to its godoc.

// Execer is an optional interface that may be implemented by a Conn.
// If a Conn does not implement Execer, the sql package's DB.Exec will
// first prepare a query, execute the statement, and then close the
// statement.
// Exec may return ErrSkip.
// Deprecated: Drivers should implement ExecerContext instead (or additionally).
type Execer interface {
	Exec(query string, args []Value) (Result, error)

The deprecation notice should be in the godoc, begin with string “Deprecated: " and follow with a tip for replacement.

// Deprecated: Use strings.HasPrefix instead.

User are expected to follow the tip and switch to the new recommended API.

Additional to the notices, there is an effort going on to discourage users to keep depending on the deprecated APIs.

See the following items for the ongoing work:

In conclusion, please use this specific format to add deprecation notices. Not “DEPRECATED” or not “This type is deprecated”. Soon, you will be able to enjoy the tooling support that yells at your users to stop depending on your deprecated APIs.