chore: do not use sentinel errors when unneeded

- main reason being it's a burden to always define sentinel errors at global scope, wrap them with `%w` instead of using a string directly
- only use sentinel errors when it has to be checked using `errors.Is`
- replace all usage of these sentinel errors in `fmt.Errorf` with direct strings that were in the sentinel error
- exclude the sentinel error definition requirement from .golangci.yml
- update unit tests to use ContainersError instead of ErrorIs so it stays as a "not a change detector test" without requiring a sentinel error

internal/healthcheck/checker.go

@@ -266,8 +266,6 @@ func makeAddressToDial(address string) (addressToDial string, err error) {
 	return address, nil
 }
 
-var ErrAllCheckTriesFailed = errors.New("all check tries failed")
-
 func withRetries(ctx context.Context, tryTimeouts []time.Duration,
 	logger Logger, checkName string, check func(ctx context.Context, try int) error,
 ) error {
@@ -297,7 +295,7 @@ func withRetries(ctx context.Context, tryTimeouts []time.Duration,
 	for i, err := range errs {
 		errStrings[i] = fmt.Sprintf("attempt %d (%dms): %s", i+1, err.durationMS, err.err)
 	}
-	return fmt.Errorf("%w:\n\t%s", ErrAllCheckTriesFailed, strings.Join(errStrings, "\n\t"))
+	return fmt.Errorf("all check tries failed:\n\t%s", strings.Join(errStrings, "\n\t"))
 }
 
 func (c *Checker) startupCheck(ctx context.Context) error {
@@ -342,7 +340,7 @@ func (c *Checker) startupCheck(ctx context.Context) error {
 	for i, err := range errs {
 		errStrings[i] = fmt.Sprintf("parallel attempt %d/%d failed: %s", i+1, len(errs), err)
 	}
-	return fmt.Errorf("%w: %s", ErrAllCheckTriesFailed, strings.Join(errStrings, ", "))
+	return fmt.Errorf("all check tries failed: %s", strings.Join(errStrings, ", "))
 }
 
 const (

internal/healthcheck/checker_test.go

@@ -2,7 +2,6 @@ package healthcheck
 
 import (
 	"context"
-	"fmt"
 	"net"
 	"testing"
 	"time"
@@ -68,7 +67,7 @@ func Test_makeAddressToDial(t *testing.T) {
 	testCases := map[string]struct {
 		address       string
 		addressToDial string
-		err           error
+		errMessage    string
 	}{
 		"host without port": {
 			address:       "test.com",
@@ -79,8 +78,8 @@ func Test_makeAddressToDial(t *testing.T) {
 			addressToDial: "test.com:80",
 		},
 		"bad address": {
-			address: "test.com::",
-			err:     fmt.Errorf("splitting host and port from address: address test.com::: too many colons in address"), //nolint:lll
+			address:    "test.com::",
+			errMessage: "splitting host and port from address: address test.com::: too many colons in address",
 		},
 	}
 
@@ -91,8 +90,8 @@ func Test_makeAddressToDial(t *testing.T) {
 			addressToDial, err := makeAddressToDial(testCase.address)
 
 			assert.Equal(t, testCase.addressToDial, addressToDial)
-			if testCase.err != nil {
-				assert.EqualError(t, err, testCase.err.Error())
+			if testCase.errMessage != "" {
+				assert.EqualError(t, err, testCase.errMessage)
 			} else {
 				assert.NoError(t, err)
 			}

internal/healthcheck/client.go

@@ -2,15 +2,12 @@ package healthcheck
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"time"
 )
 
-var ErrHTTPStatusNotOK = errors.New("HTTP response status is not OK")
-
 type Client struct {
 	httpClient *http.Client
 }
@@ -41,6 +38,6 @@ func (c *Client) Check(ctx context.Context, url string) error {
 	if err != nil {
 		return err
 	}
-	return fmt.Errorf("%w: %d %s: %s", ErrHTTPStatusNotOK,
+	return fmt.Errorf("HTTP response status is not OK: %d %s: %s",
 		response.StatusCode, response.Status, string(b))
 }

internal/healthcheck/dns/dns.go

@@ -2,7 +2,6 @@ package dns
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"net"
 	"net/netip"
@@ -41,8 +40,6 @@ func concatAddrPorts(addrs [][]netip.AddrPort) []netip.AddrPort {
 	return result
 }
 
-var ErrLookupNoIPs = errors.New("no IPs found from DNS lookup")
-
 func (c *Client) Check(ctx context.Context) error {
 	dnsAddr := c.serverAddrs[c.dnsIPIndex].String()
 	resolver := &net.Resolver{
@@ -59,7 +56,7 @@ func (c *Client) Check(ctx context.Context) error {
 		return fmt.Errorf("with DNS server %s: %w", dnsAddr, err)
 	case len(ips) == 0:
 		c.dnsIPIndex = (c.dnsIPIndex + 1) % len(c.serverAddrs)
-		return fmt.Errorf("with DNS server %s: %w", dnsAddr, ErrLookupNoIPs)
+		return fmt.Errorf("with DNS server %s: no IPs found from DNS lookup", dnsAddr)
 	default:
 		return nil
 	}

internal/healthcheck/handler.go

@@ -12,11 +12,9 @@ type handler struct {
 	logger      Logger
 }
 
-var errHealthcheckNotRunYet = errors.New("healthcheck did not run yet")
-
 func newHandler(logger Logger) *handler {
 	return &handler{
-		healthErr: errHealthcheckNotRunYet,
+		healthErr: errors.New("healthcheck did not run yet"),
 		logger:    logger,
 	}
 }

internal/healthcheck/icmp/echo.go

@@ -19,11 +19,6 @@ import (
 	"golang.org/x/net/ipv6"
 )
 
-var (
-	ErrICMPBodyUnsupported  = errors.New("ICMP body type is not supported")
-	ErrICMPEchoDataMismatch = errors.New("ICMP data mismatch")
-)
-
 type Echoer struct {
 	buffer       []byte
 	randomSource io.Reader
@@ -60,10 +55,7 @@ func (e *Echoer) Reset() {
 	e.seqStart = time.Now()
 }
 
-var (
-	ErrTimedOut     = errors.New("timed out waiting for ICMP echo reply")
-	ErrNotPermitted = errors.New("not permitted")
-)
+var ErrNotPermitted = errors.New("not permitted")
 
 func (e *Echoer) Echo(ctx context.Context, ip netip.Addr) (err error) {
 	var ipVersion string
@@ -114,14 +106,14 @@ func (e *Echoer) Echo(ctx context.Context, ip netip.Addr) (err error) {
 	receivedData, err := receiveEchoReply(conn, e.id, e.seq, e.buffer, ipVersion, e.logger)
 	if err != nil {
 		if errors.Is(err, net.ErrClosed) && ctx.Err() != nil {
-			return fmt.Errorf("%w from %s", ErrTimedOut, ip)
+			return fmt.Errorf("timed out waiting for ICMP echo reply from %s", ip)
 		}
 		return fmt.Errorf("receiving ICMP echo reply from %s: %w", ip, err)
 	}
 
 	sentData := message.Body.(*icmp.Echo).Data //nolint:forcetypeassert
 	if !bytes.Equal(receivedData, sentData) {
-		return fmt.Errorf("%w: sent %x to %s and received %x", ErrICMPEchoDataMismatch, sentData, ip, receivedData)
+		return fmt.Errorf("ICMP data mismatch: sent %x to %s and received %x", sentData, ip, receivedData)
 	}
 
 	return nil
@@ -216,8 +208,9 @@ func receiveEchoReply(conn net.PacketConn, id, seq int, buffer []byte, ipVersion
 				message.Code, returnAddr, id, seq)
 			continue
 		default:
-			return nil, fmt.Errorf("%w: %T (type %d, code %d, return address %s, expected id %d and seq %d)",
-				ErrICMPBodyUnsupported, body, message.Type, message.Code, returnAddr, id, seq)
+			return nil, fmt.Errorf("ICMP body type is not supported: "+
+				"%T (type %d, code %d, return address %s, expected id %d and seq %d)",
+				body, message.Type, message.Code, returnAddr, id, seq)
 		}
 	}
 }