Issue #130 Update Go up to 1.16.4

[ivan1993spb]

• Update Go up to 1.16.4 in .travis.yml
• Update Go up to 1.16.4 in Dockerfile
• Update Go up to 1.16.4 in Makefile
• Update Go up to 1.16.4 reminder in README.md
• Update Go up to 1.16.4 in go mod files