The package author means the error will be nil when the secret is 32 characters long; he doesn't mean you can completely ignore checking it.
Regarding when to use panic:
"The convention in the Go libraries is that even when a package uses panic internally, its external API still presents explicit error return values." http://blog.golang.org/defer-panic-and-recover
Panics should only be used in cases of programmer error or when the process is in an unrecoverable state.
The package author means the error will be nil when the secret is 32 characters long; he doesn't mean you can completely ignore checking it.
Regarding when to use panic: "The convention in the Go libraries is that even when a package uses panic internally, its external API still presents explicit error return values." http://blog.golang.org/defer-panic-and-recover
Panics should only be used in cases of programmer error or when the process is in an unrecoverable state.