staticcheck (#313)

* CI: use staticcheck for linting

This commit switches the linter for Go code from golint to staticcheck.
Golint has been deprecated since last year and staticcheck is a
recommended replacement.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* revendor

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* cmd,pkg: fix lint warnings

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

vendor/github.com/BurntSushi/toml/doc.go

@@ -0,0 +1,13 @@
+/*
+Package toml implements decoding and encoding of TOML files.
+
+This package supports TOML v1.0.0, as listed on https://toml.io
+
+There is also support for delaying decoding with the Primitive type, and
+querying the set of keys in a TOML document with the MetaData type.
+
+The github.com/BurntSushi/toml/cmd/tomlv package implements a TOML validator,
+and can be used to verify if TOML document is valid. It can also be used to
+print the type of each key.
+*/
+package toml