fix: use github.com/alecthomas/errors instead of stdlib errors/fmt.Errorf

.golangci.yml

@@ -1,3 +1,5 @@
+# yaml-language-server: $schema=https://golangci-lint.run/jsonschema/golangci.v2.jsonschema.json
+#
 # This file is licensed under the terms of the MIT license https://opensource.org/license/mit
 # Copyright (c) 2021-2025 Marat Reimers
 
@@ -217,6 +219,12 @@ linters:
           deny:
             - pkg: log$
               desc: Use log/slog instead, see https://go.dev/blog/slog
+        "errors":
+          deny:
+            - pkg: ^errors$
+              desc: Use github.com/alecthomas/errors instead
+            - pkg: ^github.com/pkg/errors$
+              desc: Use github.com/alecthomas/errors instead
 
     embeddedstructfieldcheck:
       # Checks that sync.Mutex and sync.RWMutex are not used as embedded fields.
@@ -434,6 +442,16 @@ linters:
       ignore-package-globs:
         - "github.com/alecthomas/errors"
 
+    forbidigo:
+      exclude-godoc-examples: true
+      analyze-types: true
+      forbid:
+        - pkg: ^fmt$
+          pattern: ^fmt\.Errorf$
+          msg: "Use github.com/alecthomas/errors.Errorf instead"
+        - pkg: "^errors$"
+          msg: "Use github.com/alecthomas/errors instead"
+
   exclusions:
     # Predefined exclusion rules.
     # Default: []

cmd/cachewd/main.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/alecthomas/chroma/v2/quick"
+	"github.com/alecthomas/errors"
 	"github.com/alecthomas/hcl/v2"
 	"github.com/alecthomas/kong"
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
@@ -149,7 +150,7 @@ func newMux(ctx context.Context, cr *cache.Registry, sr *strategy.Registry, prov
 	})
 
 	if err := config.Load(ctx, cr, sr, providersConfigHCL, mux, vars); err != nil {
-		return nil, fmt.Errorf("load config: %w", err)
+		return nil, errors.Errorf("load config: %w", err)
 	}
 
 	return mux, nil
@@ -205,7 +206,7 @@ func loadGlobalConfig(ast *hcl.AST) (GlobalConfig, map[string]string, error) {
 	var cfg GlobalConfig
 	schema, err := hcl.Schema(&cfg)
 	if err != nil {
-		return cfg, nil, fmt.Errorf("global config schema: %w", err)
+		return cfg, nil, errors.Errorf("global config schema: %w", err)
 	}
 	envars := parseEnvars()
 	config.InjectEnvars(schema, ast, "CACHEW", envars)
@@ -220,7 +221,7 @@ func loadGlobalConfig(ast *hcl.AST) (GlobalConfig, map[string]string, error) {
 		})
 	})
 	if err := hcl.UnmarshalAST(ast, &cfg, hcl.HydratedImplicitBlocks(true), preserving); err != nil {
-		return cfg, nil, fmt.Errorf("load global config: %w", err)
+		return cfg, nil, errors.Errorf("load global config: %w", err)
 	}
 
 	// Inject state directory as CACHEW_STATE for provider config expansion.
@@ -232,7 +233,7 @@ func loadGlobalConfig(ast *hcl.AST) (GlobalConfig, map[string]string, error) {
 		return os.Expand(s, func(key string) string { return envars[key] })
 	})
 	if err := hcl.UnmarshalAST(ast, &cfg, hcl.HydratedImplicitBlocks(true), expanding); err != nil {
-		return cfg, nil, fmt.Errorf("load global config: %w", err)
+		return cfg, nil, errors.Errorf("load global config: %w", err)
 	}
 	return cfg, envars, nil
 }

internal/cache/cachetest/soak.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"crypto/rand"
 	"crypto/sha256"
-	"errors"
 	"fmt"
 	"io"
 	mrand "math/rand/v2"
@@ -17,6 +16,7 @@ import (
 	"time"
 
 	"github.com/alecthomas/assert/v2"
+	"github.com/alecthomas/errors"
 
 	"github.com/block/cachew/internal/cache"
 )

internal/cache/cachetest/suite.go

@@ -2,14 +2,14 @@ package cachetest
 
 import (
 	"context"
-	"errors"
 	"io"
 	"net/http"
 	"os"
 	"testing"
 	"time"
 
 	"github.com/alecthomas/assert/v2"
+	"github.com/alecthomas/errors"
 
 	"github.com/block/cachew/internal/cache"
 )

internal/metrics/metrics.go

@@ -2,11 +2,11 @@ package metrics
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"net/http"
 	"time"
 
+	"github.com/alecthomas/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"go.opentelemetry.io/otel"
@@ -61,7 +61,7 @@ func New(ctx context.Context, cfg Config) (*Client, error) {
 		resource.WithHost(),
 	)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create resource: %w", err)
+		return nil, errors.Errorf("failed to create resource: %w", err)
 	}
 
 	var readers []sdkmetric.Reader
@@ -74,7 +74,7 @@ func New(ctx context.Context, cfg Config) (*Client, error) {
 		registry = prometheus.NewRegistry()
 		prometheusExporter, err = prometheusexporter.New(prometheusexporter.WithRegisterer(registry))
 		if err != nil {
-			return nil, fmt.Errorf("failed to create Prometheus exporter: %w", err)
+			return nil, errors.Errorf("failed to create Prometheus exporter: %w", err)
 		}
 		readers = append(readers, prometheusExporter)
 		exporters = append(exporters, "prometheus")
@@ -91,7 +91,7 @@ func New(ctx context.Context, cfg Config) (*Client, error) {
 
 		otlpExporter, err := otlpmetrichttp.New(ctx, opts...)
 		if err != nil {
-			return nil, fmt.Errorf("failed to create OTLP exporter: %w", err)
+			return nil, errors.Errorf("failed to create OTLP exporter: %w", err)
 		}
 
 		// Create periodic reader for OTLP
@@ -140,7 +140,7 @@ func (c *Client) Close() error {
 	}
 	if provider, ok := c.provider.(*sdkmetric.MeterProvider); ok {
 		if err := provider.Shutdown(context.Background()); err != nil {
-			return fmt.Errorf("failed to shutdown meter provider: %w", err)
+			return errors.Errorf("failed to shutdown meter provider: %w", err)
 		}
 	}
 	return nil

internal/strategy/apiv1.go

@@ -3,14 +3,15 @@ package strategy
 import (
 	"context"
 	"encoding/json"
-	"errors"
 	"io"
 	"log/slog"
 	"maps"
 	"net/http"
 	"os"
 	"time"
 
+	"github.com/alecthomas/errors"
+
 	"github.com/block/cachew/internal/cache"
 	"github.com/block/cachew/internal/logging"
 )

internal/strategy/artifactory.go

@@ -2,13 +2,14 @@ package strategy
 
 import (
 	"context"
-	"fmt"
 	"log/slog"
 	"net/http"
 	"net/url"
 	"slices"
 	"strings"
 
+	"github.com/alecthomas/errors"
+
 	"github.com/block/cachew/internal/cache"
 	"github.com/block/cachew/internal/logging"
 	"github.com/block/cachew/internal/strategy/handler"
@@ -55,7 +56,7 @@ var _ Strategy = (*Artifactory)(nil)
 func NewArtifactory(ctx context.Context, config ArtifactoryConfig, cache cache.Cache, mux Mux) (*Artifactory, error) {
 	u, err := url.Parse(config.Target)
 	if err != nil {
-		return nil, fmt.Errorf("invalid target URL: %w", err)
+		return nil, errors.Errorf("invalid target URL: %w", err)
 	}
 
 	a := &Artifactory{
@@ -117,7 +118,7 @@ func (a *Artifactory) transformRequest(r *http.Request) (*http.Request, error) {
 
 	req, err := http.NewRequestWithContext(r.Context(), http.MethodGet, targetURL.String(), nil)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create request: %w", err)
+		return nil, errors.Errorf("failed to create request: %w", err)
 	}
 
 	// Pass through authentication headers

internal/strategy/gomod/cacher.go

@@ -2,11 +2,12 @@ package gomod
 
 import (
 	"context"
-	"fmt"
 	"io"
 	"io/fs"
 	"strings"
 
+	"github.com/alecthomas/errors"
+
 	"github.com/block/cachew/internal/cache"
 )
 
@@ -34,20 +35,20 @@ func (g *goproxyCacher) Put(ctx context.Context, name string, content io.ReadSee
 
 	wc, err := g.cache.Create(ctx, key, nil, 0)
 	if err != nil {
-		return fmt.Errorf("create cache entry: %w", err)
+		return errors.Errorf("create cache entry: %w", err)
 	}
 	defer wc.Close()
 
 	if _, err := content.Seek(0, io.SeekStart); err != nil {
-		return fmt.Errorf("seek to start: %w", err)
+		return errors.Errorf("seek to start: %w", err)
 	}
 
 	if _, err := io.Copy(wc, content); err != nil {
-		return fmt.Errorf("write to cache: %w", err)
+		return errors.Errorf("write to cache: %w", err)
 	}
 
 	if err := wc.Close(); err != nil {
-		return fmt.Errorf("close cache entry: %w", err)
+		return errors.Errorf("close cache entry: %w", err)
 	}
 
 	return nil

internal/strategy/gomod/gomod.go

@@ -2,13 +2,12 @@ package gomod
 
 import (
 	"context"
-	"errors"
-	"fmt"
 	"log/slog"
 	"net/http"
 	"net/url"
 	"os/exec"
 
+	"github.com/alecthomas/errors"
 	"github.com/goproxy/goproxy"
 
 	"github.com/block/cachew/internal/cache"
@@ -48,12 +47,12 @@ func New(ctx context.Context, config Config, cache cache.Cache, mux strategy.Mux
 
 	parsedURL, err := url.Parse(config.Proxy)
 	if err != nil {
-		return nil, fmt.Errorf("invalid proxy URL: %w", err)
+		return nil, errors.Errorf("invalid proxy URL: %w", err)
 	}
 
 	cloneManager, err := cloneManagerProvider()
 	if err != nil {
-		return nil, fmt.Errorf("failed to create clone manager: %w", err)
+		return nil, errors.Errorf("failed to create clone manager: %w", err)
 	}
 
 	s := &Strategy{

internal/strategy/host.go

@@ -2,11 +2,12 @@ package strategy
 
 import (
 	"context"
-	"fmt"
 	"log/slog"
 	"net/http"
 	"net/url"
 
+	"github.com/alecthomas/errors"
+
 	"github.com/block/cachew/internal/cache"
 	"github.com/block/cachew/internal/logging"
 	"github.com/block/cachew/internal/strategy/handler"
@@ -43,7 +44,7 @@ var _ Strategy = (*Host)(nil)
 func NewHost(ctx context.Context, config HostConfig, cache cache.Cache, mux Mux) (*Host, error) {
 	u, err := url.Parse(config.Target)
 	if err != nil {
-		return nil, fmt.Errorf("invalid target URL: %w", err)
+		return nil, errors.Errorf("invalid target URL: %w", err)
 	}
 	prefix := "/" + u.Host + u.EscapedPath()
 	h := &Host{