auth: detection of unset EXPERIMENTAL_GOOGLE_API_USE_S2A fails

[quartzmo]

Module

auth

Go Environment

go1.22.0 darwin/amd64

Code

Previous:

https://github.com/googleapis/google-api-go-client/blob/v0.172.0/internal/cba.go#L316-L318

	if !isGoogleS2AEnabled() {
		return false
	}

func isGoogleS2AEnabled() bool {
	return strings.ToLower(os.Getenv(googleAPIUseS2AEnv)) == "true"
}

Current:

https://github.com/googleapis/google-cloud-go/blob/auth/v0.1.1/auth/internal/transport/s2a.go#L164-L167

	if b, err := strconv.ParseBool(os.Getenv(googleAPIUseS2AEnv)); err == nil && !b {
		return false
	}

Expected behavior

If EXPERIMENTAL_GOOGLE_API_USE_S2A is not set, returns false.

Actual behavior

If EXPERIMENTAL_GOOGLE_API_USE_S2A is not set, execution continues.

If err and b are captured and logged, values are:

err:  strconv.ParseBool: parsing "": invalid syntax
b:  false

Possible solutions

1. Remove err == nil && and ignore error?
2. Restore the previous solution?