1. Specify the API at the beginning of the title (for example, "BigQuery: ...")
   General, Core, and Other are also allowed as types
   ✅
2. OS type and version
   I use the Storage lib inside a Cloud Function (Python Beta runntime)
3. Python version and virtual environment information python --version
   3.7
4. google-cloud-python version pip show google-cloud, pip show google-<service> or pip freeze
   1.12.0
5. Stacktrace if available
   ❌
6. Steps to reproduce
   ❌
7. Code example
   👇

Hey guys 👋
currently I experiment a little bit with the Cloud Storage library inside a Cloud Function.
For testing I want to make an already uploaded file available via Blob#generate_signed_url.
The thing is - it works. I have no issues.
But Yesterday I spend at least 6 hours for testing it because the method in the generated_signed_url needs to be in uppercase.
Meaning the following does not work:

blob.generate_signed_url(timedelta(minutes=5), "get")

but this works:

blob.generate_signed_url(timedelta(minutes=5), "GET")

After a quick look into your code I found out that you "just put" the string into the generated URL. Without validating if that is a valid HTTP-Method!
https://github.com/GoogleCloudPlatform/google-cloud-python/blob/81bc5ef11d1918580f41e9f8ee2c9be2529b1169/storage/google/cloud/storage/_signing.py#L189

I would recommend (or request with this issue 🙃 ) to either:

• Check if the given string is a valid HTTP-Method (POST, GET, PUT etc.) and make the string to uppercase!
• Or better (but leads to breaking changes (maybe 😃)) make an ENUM of it and only allow to put an enum-value into the method.