diff --git a/cmd/token_tesla.go b/cmd/token_tesla.go
index d35f2e663..82cc1ac21 100644
--- a/cmd/token_tesla.go
+++ b/cmd/token_tesla.go
@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"strings"
 
@@ -82,7 +81,8 @@ func codePrompt(ctx context.Context, devices []tesla.Device) (tesla.Device, stri
 }
 
 func captchaPrompt(ctx context.Context, svg io.Reader) (string, error) {
-	tmpFile, err := ioutil.TempFile(os.TempDir(), "evcc-*.svg")
+	// tmpFile, err := ioutil.TempFile(os.TempDir(), "evcc-*.svg")
+	tmpFile, err := os.CreateTemp(os.TempDir(), "evcc-*.svg")
 	if err != nil {
 		return "", fmt.Errorf("cannot create temp file: %w", err)
 	}
diff --git a/detect/tasks/modbus.go b/detect/tasks/modbus.go
index 568d3ea69..796145ca0 100644
--- a/detect/tasks/modbus.go
+++ b/detect/tasks/modbus.go
@@ -4,6 +4,8 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"net"
+	"strconv"
 	"time"
 
 	"github.com/evcc-io/evcc/util"
@@ -30,7 +32,7 @@ type ModbusResult struct {
 func (r *ModbusResult) Configuration(handler TaskHandler, res Result) map[string]interface{} {
 	port := handler.(*ModbusHandler).Port
 	cc := map[string]interface{}{
-		"uri":   fmt.Sprintf("%s:%d", res.ResultDetails.IP, port),
+		"uri":   net.JoinHostPort(res.ResultDetails.IP, strconv.Itoa(port)),
 		"model": "sunspec",
 		"id":    r.SlaveID,
 	}
@@ -179,7 +181,7 @@ func (h *ModbusHandler) Test(log *util.Logger, in ResultDetails) (res []ResultDe
 		panic("modbus: invalid port")
 	}
 
-	addr := fmt.Sprintf("%s:%d", in.IP, port)
+	addr := net.JoinHostPort(in.IP, strconv.Itoa(port))
 	conn := meters.NewTCP(addr)
 	dev := sunspec.NewDevice("sunspec")
 
diff --git a/detect/tasks/mqtt.go b/detect/tasks/mqtt.go
index 3e8f450f7..9d3bda4e2 100644
--- a/detect/tasks/mqtt.go
+++ b/detect/tasks/mqtt.go
@@ -2,7 +2,8 @@ package tasks
 
 import (
 	"errors"
-	"fmt"
+	"net"
+	"strconv"
 	"time"
 
 	mqtt "github.com/eclipse/paho.mqtt.golang"
@@ -36,10 +37,10 @@ type MqttHandler struct {
 }
 
 func (h *MqttHandler) Test(log *util.Logger, in ResultDetails) []ResultDetails {
-	broker := fmt.Sprintf("%s:%d", in.IP, h.Port)
+	addr := net.JoinHostPort(in.IP, strconv.Itoa(h.Port))
 
 	opt := mqtt.NewClientOptions()
-	opt.AddBroker(broker)
+	opt.AddBroker(addr)
 	opt.SetConnectTimeout(timeout)
 
 	client := mqtt.NewClient(opt)
diff --git a/detect/tasks/tcp.go b/detect/tasks/tcp.go
index 4bd4bf82e..76d4fab56 100644
--- a/detect/tasks/tcp.go
+++ b/detect/tasks/tcp.go
@@ -2,8 +2,8 @@ package tasks
 
 import (
 	"errors"
-	"fmt"
 	"net"
+	"strconv"
 	"time"
 
 	"github.com/evcc-io/evcc/util"
@@ -37,7 +37,7 @@ type TcpHandler struct {
 
 func (h *TcpHandler) Test(log *util.Logger, in ResultDetails) (res []ResultDetails) {
 	for _, port := range h.Ports {
-		addr := fmt.Sprintf("%s:%d", in.IP, port)
+		addr := net.JoinHostPort(in.IP, strconv.Itoa(port))
 		conn, err := h.dialer.Dial("tcp", addr)
 		if err == nil {
 			defer conn.Close()
diff --git a/server/uds.go b/server/uds.go
index 4b40bda59..f775057af 100644
--- a/server/uds.go
+++ b/server/uds.go
@@ -4,6 +4,7 @@
 package server
 
 import (
+	"errors"
 	"net"
 	"net/http"
 	"os"
@@ -21,7 +22,7 @@ func removeIfExists(file string) {
 		err = os.Remove(file)
 	}
 
-	if err != nil && !os.IsNotExist(err) {
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
 		log.FATAL.Fatal(err)
 	}
 }
diff --git a/server/updater/gokrazy.go b/server/updater/gokrazy.go
index 7f97e9361..7eb33f258 100644
--- a/server/updater/gokrazy.go
+++ b/server/updater/gokrazy.go
@@ -1,3 +1,4 @@
+//go:build gokrazy
 // +build gokrazy
 
 package updater
@@ -29,7 +30,7 @@ var (
 // unzipReader transparently unpacks zip files
 func unzipReader(file io.ReadCloser) (io.ReadCloser, error) {
 	if unzipped, err := gzip.NewReader(file); err == nil {
-		return unzipped, err
+		return unzipped, nil
 	}
 
 	return file, nil
diff --git a/util/net.go b/util/net.go
index e9224dd0a..f61a9509f 100644
--- a/util/net.go
+++ b/util/net.go
@@ -4,13 +4,14 @@ import (
 	"fmt"
 	"net"
 	"net/url"
+	"strconv"
 	"strings"
 )
 
 // DefaultPort appends given port to connection if not specified
 func DefaultPort(conn string, port int) string {
 	if _, _, err := net.SplitHostPort(conn); err != nil {
-		conn = fmt.Sprintf("%s:%d", conn, port)
+		conn = net.JoinHostPort(conn, strconv.Itoa(port))
 	}
 
 	return conn
diff --git a/vehicle/ovms.go b/vehicle/ovms.go
index 4732b5630..969fecd1b 100644
--- a/vehicle/ovms.go
+++ b/vehicle/ovms.go
@@ -230,7 +230,7 @@ func (v *Ovms) FinishTime() (time.Time, error) {
 	if res, ok := res.(ovmsChargeResponse); err == nil && ok {
 		cef, err := strconv.ParseInt(res.ChargeEtrFull, 0, 64)
 		if err == nil {
-			return time.Now().Add(time.Duration(cef) * time.Minute), err
+			return time.Now().Add(time.Duration(cef) * time.Minute), nil
 		}
 	}