Upgrade min Go version to 1.16 and replace ioutil

[abhinavnair]

The intention of PR is to replace the ioutil pkg which was deprecated in 1.16. But to do that, first had to upgrade the minimum supported Go version to 1.16. This should not be an issue for anyone because this entire pkg is mainly used by gqlgen which already has min. support of 1.16 Please do share any concerns if you have.

Contents:-

• Increase minimum Go version supported to 1.16 to match that of gqlgen
• Upgrade all dependencies:-
  • Upgrade go-spew to v1.1.1 (latest)
  • Upgrade pkg/errors to v0.9.1 (latest)
  • Upgrade testify to v1.7.0 (latest)
  • Upgrade golang.org/x/tools to v0.1.10 (latest is v0.1.11 but it was released in June 2022 and I feel we give it some more time to stabilize before we ugprade dataloaden, especially since dataloaden is not as well maintained as gqlgen).

[abhinavnair]

@StevenACoffman not sure if you are the best person to reach out to for this repo, since I am not sure about who is the maintainer for this repo now, but this PR is following https://github.com/99designs/gqlgen/pull/2254.