Go Command Framework

This is a framework to create well-behaving commands.

Features

Go 1.11 or later, though the code is expected to work with Go 1.7.

Commands using this framework implement these external specifications:

-logfile FILE

Output logs to FILE instead of standard error.
-loglevel LEVEL

Change logging threshold to LEVEL. Default is info.
LEVEL is one of critical, error, warning, info, or debug.
-logformat FORMAT

Change log formatter. Default is plain.
FORMAT is one of plain, logfmt, or json.

SIGUSR1

If -logfile is specified, this signal make the program reopen
the log file to cooperate with an external log rotation program.

On Windows, this is not implemented.
SIGINT and SIGTERM

These signals cancel the context of the global environment,
and hence goroutines registered with the environment. Usually
this will result in graceful stop of network servers, if any.

On Windows, only SIGINT is handled.
SIGHUP

This signal is used to restart network servers gracefully.
Internally, the main (master) process restarts its child process.
The PID of the master process thus will not change.

There is one limitation: the location of log file cannot be changed
by graceful restart. To change log file location, the server need
to be (gracefully) stopped and started.

On Windows, this is not implemented.
SIGPIPE

The framework changes the way Go handles SIGPIPE slightly.
If a program using this framework receives SIGPIPE when writing to stdout or stderr, the program exits with status code 2.
See #15 for details.

REQUEST_ID_HEADER

The value of this variable is used as HTTP header name.
The HTTP header is used to track activities across services.
The default header name is "X-Cybozu-Request-ID".
CYBOZU_LISTEN_FDS

This is used internally for graceful restart.

Pull requests are welcome to add your project to this list!