Update golangci config (#3343)

`deadline` is now deprecated in favor of `timeout` and currently breaks
CI.
The other changes remove some warnings produced.

.golangci.yml

@@ -6,7 +6,7 @@ run:
   concurrency: 4
 
   # timeout for analysis, e.g. 30s, 5m, default is 1m
-  deadline: 30m
+  timeout: 5m
 
   # exit code when at least one issue was found, default is 1
   issues-exit-code: 1
@@ -18,24 +18,6 @@ run:
   #build-tags:
   #  - mytag
 
-  # which dirs to skip: they won't be analyzed;
-  # can use regexp here: generated.*, regexp is applied on full path;
-  # default value is empty list, but next dirs are always skipped independently
-  # from this option's value:
-  #   	vendor$, third_party$, testdata$, examples$, Godeps$, builtin$
-  skip-dirs:
-    - bin
-    - docs
-
-  # which files to skip: they will be analyzed, but issues from them
-  # won't be reported. Default value is empty list, but there is
-  # no need to include all autogenerated files, we confidently recognize
-  # autogenerated files. If it's not please let us know.
-  skip-files:
-    - ".*\\.md$"
-    - ".*\\.sh$"
-    - "^cmd/syncserver-integration-tests/testdata.go$"
-
   # by default isn't set. If set we pass it to "go list -mod={option}". From "go help modules":
   # If invoked with -mod=readonly, the go command is disallowed from the implicit
   # automatic updating of go.mod described above. Instead, it fails when any changes
@@ -50,7 +32,8 @@ run:
 # output configuration options
 output:
   # colored-line-number|line-number|json|tab|checkstyle|code-climate, default is "colored-line-number"
-  format: colored-line-number
+  formats:
+    - format: colored-line-number
 
   # print lines of code with issue, default is true
   print-issued-lines: true
@@ -79,9 +62,8 @@ linters-settings:
     # see https://github.com/kisielk/errcheck#excluding-functions for details
     #exclude: /path/to/file.txt
   govet:
-    # report about shadowed variables
-    check-shadowing: true
-
+    enable:
+      - shadow
     # settings per analyzer
     settings:
       printf: # analyzer name, run `go tool vet help` to see all analyzers
@@ -217,6 +199,24 @@ linters:
 
 
 issues:
+  # which files to skip: they will be analyzed, but issues from them
+  # won't be reported. Default value is empty list, but there is
+  # no need to include all autogenerated files, we confidently recognize
+  # autogenerated files. If it's not please let us know.
+  exclude-files:
+    - ".*\\.md$"
+    - ".*\\.sh$"
+    - "^cmd/syncserver-integration-tests/testdata.go$"
+
+  # which dirs to skip: they won't be analyzed;
+  # can use regexp here: generated.*, regexp is applied on full path;
+  # default value is empty list, but next dirs are always skipped independently
+  # from this option's value:
+  #   	vendor$, third_party$, testdata$, examples$, Godeps$, builtin$
+  exclude-dirs:
+    - bin
+    - docs
+
   # List of regexps of issue texts to exclude, empty list by default.
   # But independently from this option we use default exclude patterns,
   # it can be disabled by `exclude-use-default: false`. To list all