Add note about how to use ~/.aws configurations

[olgabot]

Hello! I'm trying out Go for a project. I ran into some issues with getting Reflow going and found this thread about using AWS credentials, which fixed my problem. This PR adds the text from the issue thread into the README for newcomers.

[mariusae]

Thanks! Pulling these internally; should be pushed to GitHub again soon.

[mariusae]

I think the better fix here is to make this the default. I think most users would expect AWS configuration to be loaded...

[mariusae]

Reading through the code, it does look as if we're already doing this, but only for credentials.

So the fix is to also load region configuration, etc. from the shared configuration.

[mariusae]

Something like this appears to work:

diff --git a/go/src/github.com/grailbio/reflow/config/awsenvconfig/aws.go b/go/src/github.com/grailbio/reflow/config/awsenvconfig/aws.go
index 63963e6cee..520dcabcfe 100644
--- a/go/src/github.com/grailbio/reflow/config/awsenvconfig/aws.go
+++ b/go/src/github.com/grailbio/reflow/config/awsenvconfig/aws.go
@@ -148,8 +148,11 @@ func (c *credentialsSession) AWS() (*session.Session, error) {
            c.err = fmt.Errorf("failed to retrieve AWS credentials: %v", err)
            return
        }
-       c.session, c.err = session.NewSession(&aws.Config{
-           Credentials: credentials.NewCredentials(credProvider),
+       c.session, c.err = session.NewSessionWithOptions(session.Options{
+           Config: aws.Config{
+               Credentials: credentials.NewCredentials(credProvider),
+           },
+           SharedConfigState: session.SharedConfigEnable,
        })
    })
    return c.session, c.err

[mariusae]

(I'll get this through internally; should show up here soon.)

[mariusae]

Fixed in https://github.com/grailbio/reflow/commit/8ec7db690adc615494b8b71f0cb7a42c3c20f9c0