all: consistently use http.Method{Get,Post,Put} across the codebase

This is a follow-up after 9dec3c8f80

app/vmagent/main.go

@@ -208,7 +208,7 @@ func getAuthTokenFromPath(path string) (*auth.Token, error) {
 
 func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 	if r.URL.Path == "/" {
-		if r.Method != "GET" {
+		if r.Method != http.MethodGet {
 			return false
 		}
 		w.Header().Add("Content-Type", "text/html; charset=utf-8")

app/vmagent/prometheusimport/request_handler_test.go

@@ -23,7 +23,7 @@ var (
 func TestInsertHandler(t *testing.T) {
 	setUp()
 	defer tearDown()
-	req := httptest.NewRequest("POST", "/insert/0/api/v1/import/prometheus", bytes.NewBufferString(`{"foo":"bar"}
+	req := httptest.NewRequest(http.MethodPost, "/insert/0/api/v1/import/prometheus", bytes.NewBufferString(`{"foo":"bar"}
 go_memstats_alloc_bytes_total 1`))
 	if err := InsertHandler(nil, req); err != nil {
 		t.Errorf("unxepected error %s", err)

app/vmalert/web.go

@@ -57,7 +57,7 @@ func (rh *requestHandler) handler(w http.ResponseWriter, r *http.Request) bool {
 
 	switch r.URL.Path {
 	case "/", "/vmalert", "/vmalert/":
-		if r.Method != "GET" {
+		if r.Method != http.MethodGet {
 			httpserver.Errorf(w, r, "path %q supports only GET method", r.URL.Path)
 			return false
 		}

app/vmauth/main.go

@@ -169,7 +169,7 @@ func tryProcessingRequest(w http.ResponseWriter, r *http.Request, targetURL *url
 	if err != nil {
 		remoteAddr := httpserver.GetQuotedRemoteAddr(r)
 		requestURI := httpserver.GetRequestURI(r)
-		if r.Method == "POST" || r.Method == "PUT" {
+		if r.Method == http.MethodPost || r.Method == http.MethodPut {
 			// It is impossible to retry POST and PUT requests,
 			// since we already proxied the request body to the backend.
 			err = &httpserver.ErrorWithStatusCode{

app/vmctl/vm_native.go

@@ -147,7 +147,7 @@ func (p *vmNativeProcessor) runSingle(ctx context.Context, f filter, srcURL, dst
 	sync := make(chan struct{})
 	go func() {
 		defer func() { close(sync) }()
-		req, err := http.NewRequestWithContext(ctx, "POST", dstURL, pr)
+		req, err := http.NewRequestWithContext(ctx, http.MethodPost, dstURL, pr)
 		if err != nil {
 			log.Fatalf("cannot create import request to %q: %s", p.dst.addr, err)
 		}
@@ -198,7 +198,7 @@ func (p *vmNativeProcessor) runSingle(ctx context.Context, f filter, srcURL, dst
 
 func (p *vmNativeProcessor) getSourceTenants(ctx context.Context, f filter) ([]string, error) {
 	u := fmt.Sprintf("%s/%s", p.src.addr, nativeTenantsAddr)
-	req, err := http.NewRequestWithContext(ctx, "GET", u, nil)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create request to %q: %s", u, err)
 	}
@@ -232,7 +232,7 @@ func (p *vmNativeProcessor) getSourceTenants(ctx context.Context, f filter) ([]s
 }
 
 func (p *vmNativeProcessor) exportPipe(ctx context.Context, url string, f filter) (io.ReadCloser, error) {
-	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create request to %q: %s", p.src.addr, err)
 	}

app/vminsert/main.go

@@ -188,7 +188,7 @@ func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 	defer requestDuration.UpdateDuration(startTime)
 
 	if r.URL.Path == "/" {
-		if r.Method != "GET" {
+		if r.Method != http.MethodGet {
 			return false
 		}
 		fmt.Fprintf(w, "vminsert - a component of VictoriaMetrics cluster. See docs at https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html")

app/vmselect/main.go

@@ -177,7 +177,7 @@ var (
 
 func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 	if r.URL.Path == "/" {
-		if r.Method != "GET" {
+		if r.Method != http.MethodGet {
 			return false
 		}
 		fmt.Fprintf(w, `vmselect - a component of VictoriaMetrics cluster<br/>
@@ -298,7 +298,7 @@ func selectHandler(qt *querytracer.Tracer, startTime time.Time, w http.ResponseW
 		httpRequestsDuration.Get(at).Add(int(time.Since(startTime).Milliseconds()))
 	}()
 	if p.Suffix == "" {
-		if r.Method != "GET" {
+		if r.Method != http.MethodGet {
 			return false
 		}
 		w.Header().Add("Content-Type", "text/html; charset=utf-8")

app/vmstorage/main.go

@@ -159,7 +159,7 @@ func main() {
 func newRequestHandler(strg *storage.Storage) httpserver.RequestHandler {
 	return func(w http.ResponseWriter, r *http.Request) bool {
 		if r.URL.Path == "/" {
-			if r.Method != "GET" {
+			if r.Method != http.MethodGet {
 				return false
 			}
 			fmt.Fprintf(w, "vmstorage - a component of VictoriaMetrics cluster. See docs at https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html")

lib/httpserver/httpserver.go

@@ -674,7 +674,7 @@ func WriteAPIHelp(w io.Writer, pathList [][2]string) {
 // GetRequestURI returns requestURI for r.
 func GetRequestURI(r *http.Request) string {
 	requestURI := r.RequestURI
-	if r.Method != "POST" {
+	if r.Method != http.MethodPost {
 		return requestURI
 	}
 	_ = r.ParseForm()

lib/promscrape/client.go

@@ -185,7 +185,7 @@ func newClient(sw *ScrapeWork, ctx context.Context) *client {
 func (c *client) GetStreamReader() (*streamReader, error) {
 	deadline := time.Now().Add(c.sc.Timeout)
 	ctx, cancel := context.WithDeadline(c.ctx, deadline)
-	req, err := http.NewRequestWithContext(ctx, "GET", c.scrapeURL, nil)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.scrapeURL, nil)
 	if err != nil {
 		cancel()
 		return nil, fmt.Errorf("cannot create request for %q: %w", c.scrapeURL, err)

lib/promscrape/discovery/kuma/api.go

@@ -151,7 +151,7 @@ func (cfg *apiConfig) updateTargetsLabels(ctx context.Context) error {
 		logger.Panicf("BUG: cannot marshal Kuma discovery request: %s", err)
 	}
 	updateRequestFunc := func(req *http.Request) {
-		req.Method = "POST"
+		req.Method = http.MethodPost
 		req.Body = io.NopCloser(bytes.NewReader(requestBody))
 		req.Header.Set("Accept", "application/json")
 		req.Header.Set("Content-Type", "application/json")

lib/promscrape/discoveryutils/client.go

@@ -225,7 +225,7 @@ func (c *Client) getAPIResponseWithParamsAndClientCtx(ctx context.Context, clien
 	deadline := time.Now().Add(client.ReadTimeout)
 	ctx, cancel := context.WithDeadline(ctx, deadline)
 	defer cancel()
-	req, err := http.NewRequestWithContext(ctx, "GET", u.String(), nil)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
 	if err != nil {
 		return nil, fmt.Errorf("cannot create request for %q: %w", requestURL, err)
 	}