internal

defer func(w io.Writer, flags int, p string) {
	log.SetOutput(w)
	log.SetFlags(flags)
	log.SetPrefix(p)
}(log.Writer(), log.Flags(), log.Prefix())

log.SetOutput(os.Stdout)
log.SetFlags(0)
log.SetPrefix("[logger] ")
debugLog := log.New(log.Writer(), log.Prefix(), log.Flags())

ctx := context.Background()

CheckForUpdates(ctx, debugLog, fakeContainerAPIMetadataGetter("1.4.33"), "v1.4.33")
CheckForUpdates(ctx, debugLog, fakeContainerAPIMetadataGetter("very bad error occurred"), "v1.4.33")

fmt.Println("now we should get warnings")
CheckForUpdates(ctx, debugLog, fakeContainerAPIMetadataGetter("v1.6.11"), "v1.4.33")
CheckForUpdates(ctx, debugLog, fakeContainerAPIMetadataGetter("v2.7.3"), "v2.7.3-beta")

Output:

[logger] could not get latest lightsailctl version: very bad error occurred
now we should get warnings
[logger] WARNING: You are using lightsailctl v1.4.33, but v1.6.11 is available.
To download, visit https://lightsail.aws.amazon.com/ls/docs/en_us/articles/amazon-lightsail-install-software
[logger] WARNING: You are using lightsailctl v2.7.3-beta, but v2.7.3 is available.
To download, visit https://lightsail.aws.amazon.com/ls/docs/en_us/articles/amazon-lightsail-install-software