Use HandshakeContext when possible

[benpbrown]

Feature Description

When performing an explicit TLS handshake, use the HandshakeContext method introduced in Go 1.17 instead of Handshake. The difference is that HandshakeContext will respect context deadlines or cancelation.

In a previous iteration of this connector (cloud-sql-proxy), we an issue where Handshake could hang for minutes (like five minutes): GoogleCloudPlatform/cloud-sql-proxy#986.

Alternatives Considered

I am not able to come up with a workaround as the standard library method Handshake is not cancelable (so the goroutine is hung no matter what we do).

Additional Context

Equivalent fix in cloud-sql-proxy: GoogleCloudPlatform/cloud-sql-proxy#987
Handshake line in this repo:

cloud-sql-go-connector/dialer.go

Line 231 in 2a88f23

if err := tlsConn.Handshake(); err != nil {

[enocom]

Sorry for missing this @benpbrown. I can port the same fix to the connector here.