Updating dependency management to use go modules

[cikupin]

What I do?

Update dependency management from go dep to go modules, due to several reasons:

• Go dep is now deprecated and no active development. The repository is read-only https://github.com/golang/dep
• Go modules is active by default in Go 1.13 https://golang.org/doc/go1.13#modules
• Go modules is now production ready since Go 1.14 https://golang.org/doc/go1.14#introduction
• Other Go projects are now using go modules.