The documentation mentioned using the env var GOOGLE_APPLICATION_CREDENTIALS for authenticating the API. Is there some other way where we can manually pass in this credential into the SpeechClient.Create() or similar instantiation?
Yes, you can pass in a channel which is authenticated with the right credentials.
See https://googlecloudplatform.github.io/google-cloud-dotnet/docs/faq.html#how-can-i-use-non-default-credentials-for-grpc-based-apis for an example of this. You can't pass in just the credentials, as then we'd be creating a channel for you without making it easy for you to clean the channel up later if you want to do so manually.
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Yes, you can pass in a channel which is authenticated with the right credentials.
See https://googlecloudplatform.github.io/google-cloud-dotnet/docs/faq.html#how-can-i-use-non-default-credentials-for-grpc-based-apis for an example of this. You can't pass in just the credentials, as then we'd be creating a channel for you without making it easy for you to clean the channel up later if you want to do so manually.