blob/azblob: Azure Service Connector uses a different environment variable for connection strings

[bdon]

Is your feature request related to a problem? Please describe.

For Azure Service Connector, the default connection string environment variable is named AZURE_STORAGEBLOB_CONNECTIONSTRING (see docs)

However, the azblob module reads the AZURE_STORAGE_CONNECTION_STRING environment variable:

go-cloud/blob/azureblob/azureblob.go

Line 322 in 49a4d98

connectionString := os.Getenv("AZURE_STORAGE_CONNECTION_STRING")

Describe the solution you'd like

In order for gocloud to work "out of the box" using Service Connector it needs to read from this additional environment variable. Check AZURE_STORAGE_CONNECTION_STRING first, and then check AZURE_STORAGEBLOB_CONNECTIONSTRING.

Describe alternatives you've considered

• ask Azure to make this environment variable consistent?
• In my program that uses azblob check for env var AZURE_STORAGEBLOB_CONNECTIONSTRING, and if present set AZURE_STORAGE_CONNECTION_STRING

Additional Context

previous relevant PR: #3072