update linters

Signed-off-by: Florian Wagner <h2floh@github.com>

.golangci.yaml

@@ -1,16 +1,13 @@
 linters:
     disable-all: true
     enable:
-    - deadcode
     - gocyclo
-    - golint
+    - revive
     - gofmt
     - goimports
-    - varcheck
-    - structcheck
+    - unused
     - errcheck
     - ineffassign
-    - interfacer
     - unconvert
     - goconst
     - megacheck
@@ -23,5 +20,10 @@ run:
         - ".*_test\\.go$"
     modules-download-mode: vendor
 issues:
-    exclude:
-        - ".*returns unexported type.*"  
+  exclude-rules:
+    - path: test/github.go
+      text: "var-declaration: should omit type string from declaration of var authenticatedLogin; it will be inferred from the right-hand side"
+    - path: test/github.go
+      text: "var-declaration: should drop = \"\" from declaration of var errString; it is the zero value"
+    - path: src/push.go
+      text: "error-strings: error strings should not be capitalized or end with punctuation or a newline"