Added golangci-lint configuration and prepared for the integrattion

.golangci.yml

@@ -0,0 +1,55 @@
+# options for analysis running
+run:
+  # default concurrency is a available CPU number
+  concurrency: 4
+
+  # timeout for analysis, e.g. 30s, 5m, default is 1m
+  deadline: 2m
+
+  # 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:
+    - ".*generated.*"
+    - dnsfilter/rule_to_regexp.go
+
+
+# all available settings of specific linters
+linters-settings:
+  errcheck:
+    # [deprecated] comma-separated list of pairs of the form pkg:regex
+    # the regex is used to ignore names within pkg. (default "fmt:.*").
+    # see https://github.com/kisielk/errcheck#the-deprecated-method for details
+    ignore: fmt:.*,net:SetReadDeadline,net/http:^Write
+  gocyclo:
+    min-complexity: 20
+  lll:
+    line-length: 200
+
+linters:
+  enable-all: true
+  disable:
+    - interfacer
+    - gocritic
+    - scopelint
+    - gochecknoglobals
+    - gochecknoinits
+    - prealloc
+    - maligned
+    - goconst # disabled until it's possible to configure
+  fast: true
+
+issues:
+  # 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
+  # excluded by default patterns execute `golangci-lint run --help`
+  exclude:
+    # structcheck cannot detect usages while they're there
+    - .parentalServer. is unused
+    - .safeBrowsingServer. is unused
+    # errcheck
+    - Error return value of .s.closeConn. is not checked
+    # goconst
+    - string .forcesafesearch.google.com. has 3 occurrences