Mode is a simple Golang package designed to allow code to run in debug, release, or test mode.
The idea is that code can conditional code using mode.Debug() and only perform
certain activities when the code is not in release mode.
To specify the mode to compile the code under, you use build tags.
To compile in debug mode, add -tags debug to go build.
To compile in release mode, add -tags release to go build.
By default, mode assumes the mode is release unless specified or detected
otherwise. This matches the default semantics of Go programs today.
Mode can automatically determine if the code is running via go test.
Starting with Go 1.21, the testing package can safely be imported by non-test packages,
and so that is used to call testing.Testing(). Otherwise, at runtime, mode checks
for the test flags.