Remove MySQL from CI test matrix

More pedantic error handling across the code base

Fix empty URL path component returned if request path is '/'

Set allowed headers in CORS

Fix typo in header name

Implement CORS headers.

Send headers on OPTIONS request

[skip ci] Remove go version from go.mod

Handle HEAD

Create .codecov.yml

Support HEAD and fix broken dependency (#13)

Increase wait time in TestCleanup

Update README.md

Update README.md

Revert "Use t.Parallel() in most tests"