diff --git a/.circleci/config.yml b/.circleci/config.yml
index 52c6d249..9a53eb9f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -5,6 +5,41 @@ workflows:
   build:
     jobs:
       - checkout_code
+      - lint:
+          requires:
+            - checkout_code
+          go_version: "1.12"
+          vips_version: "8.7"
+      - build:
+          name: go1.11_vips8.7
+          requires:
+            - checkout_code
+          go_version: "1.12"
+          vips_version: "8.7"
+      - build:
+          name: go1.11_vips8.6
+          requires:
+            - checkout_code
+          go_version: "1.12"
+          vips_version: "8.6"
+      - build:
+          name: go1.11_vips8.5
+          requires:
+            - checkout_code
+          go_version: "1.12"
+          vips_version: "8.5"
+      - build:
+          name: go1.11_vips8.4
+          requires:
+            - checkout_code
+          go_version: "1.12"
+          vips_version: "8.4"
+      - build:
+          name: go1.11_vips8.3
+          requires:
+            - checkout_code
+          go_version: "1.12"
+          vips_version: "8.3"
       - build:
           name: go1.11_vips8.7
           requires:
@@ -108,6 +143,32 @@ jobs:
           root: .
           paths: [.]
 
+  lint:
+    docker:
+      - image: "darthsim/imgproxy-circleci:latest"
+    working_directory: /go/src/imgproxy
+    environment:
+      BASH_ENV: "/root/.bashrc"
+    parameters:
+      go_version:
+        type: string
+      vips_version:
+        type: string
+    steps:
+      - attach_workspace:
+          at: .
+      - run:
+          name: Build imgproxy
+          command: |
+            gvm install go<< parameters.go_version >> -B
+            gvm use go<< parameters.go_version >>
+            export GOPATH=/go
+            export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/root/vips/<< parameters.vips_version >>/lib
+            export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/root/vips/<< parameters.vips_version >>/lib/pkgconfig
+            export CGO_LDFLAGS_ALLOW="-s|-w"
+            curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.16.0
+            golangci-lint run .
+
   build:
     docker:
       - image: "darthsim/imgproxy-circleci:latest"
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 00000000..911fc54e
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,22 @@
+linters:
+  fast: true
+  enable:
+    - golint
+    - govet
+    - gosimple
+    - goconst
+    - goimports
+    - staticcheck
+  disable:
+    - errcheck
+
+issues:
+  exclude-rules:
+    - path: _test\.go
+      linters:
+        - goconst
+
+    # False positives on CGO generated code
+    - linters:
+        - staticcheck
+      text: "SA4000:"
diff --git a/gcs_transport.go b/gcs_transport.go
index f3ba8906..37e37eda 100644
--- a/gcs_transport.go
+++ b/gcs_transport.go
@@ -45,7 +45,7 @@ func (t gcsTransport) RoundTrip(req *http.Request) (resp *http.Response, err err
 		ProtoMajor:    1,
 		ProtoMinor:    0,
 		Header:        make(http.Header),
-		ContentLength: reader.Size(),
+		ContentLength: reader.Attrs.Size,
 		Body:          reader,
 		Close:         true,
 		Request:       req,
diff --git a/main.go b/main.go
index b0a32cc6..e56ddd86 100644
--- a/main.go
+++ b/main.go
@@ -5,6 +5,7 @@ import (
 	"os/signal"
 	"runtime"
 	"runtime/debug"
+	"syscall"
 	"time"
 
 	"net/http"
@@ -39,7 +40,7 @@ func main() {
 	s := startServer()
 
 	stop := make(chan os.Signal, 1)
-	signal.Notify(stop, os.Interrupt, os.Kill)
+	signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
 
 	<-stop
 
diff --git a/processing_options.go b/processing_options.go
index 0cde0352..36ba6c96 100644
--- a/processing_options.go
+++ b/processing_options.go
@@ -140,8 +140,6 @@ type processingOptions struct {
 	UsedPresets []string
 }
 
-type applyOptionFunc func(po *processingOptions, args []string) error
-
 const (
 	imageURLCtxKey          = ctxKey("imageUrl")
 	processingOptionsCtxKey = ctxKey("processingOptions")
@@ -467,19 +465,19 @@ func applyBackgroundOption(po *processingOptions, args []string) error {
 	case 3:
 		po.Flatten = true
 
-		if r, err := strconv.ParseUint(args[0], 10, 8); err == nil && r >= 0 && r <= 255 {
+		if r, err := strconv.ParseUint(args[0], 10, 8); err == nil && r <= 255 {
 			po.Background.R = uint8(r)
 		} else {
 			return fmt.Errorf("Invalid background red channel: %s", args[0])
 		}
 
-		if g, err := strconv.ParseUint(args[1], 10, 8); err == nil && g >= 0 && g <= 255 {
+		if g, err := strconv.ParseUint(args[1], 10, 8); err == nil && g <= 255 {
 			po.Background.G = uint8(g)
 		} else {
 			return fmt.Errorf("Invalid background green channel: %s", args[1])
 		}
 
-		if b, err := strconv.ParseUint(args[2], 10, 8); err == nil && b >= 0 && b <= 255 {
+		if b, err := strconv.ParseUint(args[2], 10, 8); err == nil && b <= 255 {
 			po.Background.B = uint8(b)
 		} else {
 			return fmt.Errorf("Invalid background blue channel: %s", args[2])
diff --git a/processing_options_test.go b/processing_options_test.go
index c6466098..f8f47777 100644
--- a/processing_options_test.go
+++ b/processing_options_test.go
@@ -16,12 +16,14 @@ import (
 type ProcessingOptionsTestSuite struct{ MainTestSuite }
 
 func (s *ProcessingOptionsTestSuite) getRequest(url string) *fasthttp.RequestCtx {
-	req := fasthttp.Request{}
-	req.SetRequestURI(url)
-	return &fasthttp.RequestCtx{
-		Request:  req,
+	ctx := fasthttp.RequestCtx{
+		Request:  fasthttp.Request{},
 		Response: fasthttp.Response{},
 	}
+
+	ctx.Request.SetRequestURI(url)
+
+	return &ctx
 }
 
 func (s *ProcessingOptionsTestSuite) TestParseBase64URL() {
diff --git a/s3transport.go b/s3transport.go
index 4903f38b..b727950d 100644
--- a/s3transport.go
+++ b/s3transport.go
@@ -25,7 +25,10 @@ func newS3Transport() http.RoundTripper {
 		s3Conf.S3ForcePathStyle = aws.Bool(true)
 	}
 
-	sess := session.New()
+	sess, err := session.NewSession()
+	if err != nil {
+		logFatal("Can't create S3 session: %s", err)
+	}
 
 	if sess.Config.Region == nil || len(*sess.Config.Region) == 0 {
 		sess.Config.Region = aws.String("us-west-1")
diff --git a/server.go b/server.go
index ac3b5762..8601c698 100644
--- a/server.go
+++ b/server.go
@@ -262,7 +262,7 @@ func (h *httpHandler) ServeHTTP(rctx *fasthttp.RequestCtx) {
 		panic(errInvalidMethod)
 	}
 
-	if bytes.Compare(rctx.RequestURI(), healthPath) == 0 {
+	if bytes.Equal(rctx.RequestURI(), healthPath) {
 		rctx.SetStatusCode(200)
 		rctx.SetBody(imgproxyIsRunningMsg)
 		return
@@ -316,7 +316,7 @@ func (h *httpHandler) ServeHTTP(rctx *fasthttp.RequestCtx) {
 
 		rctx.Response.Header.SetBytesV("ETag", eTag)
 
-		if bytes.Compare(eTag, rctx.Request.Header.Peek("If-None-Match")) == 0 {
+		if bytes.Equal(eTag, rctx.Request.Header.Peek("If-None-Match")) {
 			respondWithNotModified(reqID, rctx)
 			return
 		}
diff --git a/webp.go b/webp.go
index b2b10ddd..b6181490 100644
--- a/webp.go
+++ b/webp.go
@@ -91,7 +91,6 @@ func decodeWebpConfig(r io.Reader) (image.Config, error) {
 
 			const alphaBit = 1 << 4
 
-			wantAlpha = buf[0] != alphaBit
 			widthMinusOne := uint32(buf[4]) | uint32(buf[5])<<8 | uint32(buf[6])<<16
 			heightMinusOne := uint32(buf[7]) | uint32(buf[8])<<8 | uint32(buf[9])<<16