chore(all): review error wrappings

- remove repetitive `cannot` and `failed` prefixes
- rename `unmarshaling` to `decoding`

internal/configuration/settings/dns.go

@@ -31,7 +31,7 @@ type DNS struct {
 func (d DNS) validate() (err error) {
 	err = d.DoT.validate()
 	if err != nil {
-		return fmt.Errorf("failed validating DoT settings: %w", err)
+		return fmt.Errorf("validating DoT settings: %w", err)
 	}
 
 	return nil

internal/configuration/settings/openvpn.go

@@ -171,7 +171,7 @@ func validateOpenVPNConfigFilepath(isCustom bool,
 	extractor := extract.New()
 	_, _, err = extractor.Data(confFile)
 	if err != nil {
-		return fmt.Errorf("failed extracting information from custom configuration file: %w", err)
+		return fmt.Errorf("extracting information from custom configuration file: %w", err)
 	}
 
 	return nil

internal/configuration/sources/env/firewall.go

@@ -73,7 +73,7 @@ func stringsToIPNets(ss []string) (ipNets []net.IPNet, err error) {
 	for i, s := range ss {
 		ip, ipNet, err := net.ParseCIDR(s)
 		if err != nil {
-			return nil, fmt.Errorf("cannot parse IP network %q: %w", s, err)
+			return nil, fmt.Errorf("parsing IP network %q: %w", s, err)
 		}
 		ipNet.IP = ip
 		ipNets[i] = *ipNet

internal/configuration/sources/env/helpers.go

@@ -137,7 +137,7 @@ func unsetEnvKeys(envKeys []string, err error) (newErr error) {
 	for _, envKey := range envKeys {
 		unsetErr := os.Unsetenv(envKey)
 		if unsetErr != nil && newErr == nil {
-			newErr = fmt.Errorf("cannot unset environment variable %s: %w", envKey, unsetErr)
+			newErr = fmt.Errorf("unsetting environment variable %s: %w", envKey, unsetErr)
 		}
 	}
 	return newErr

internal/configuration/sources/secrets/httpproxy.go

@@ -12,7 +12,7 @@ func readHTTPProxy() (settings settings.HTTPProxy, err error) {
 		"/run/secrets/httpproxy_user",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read HTTP proxy user secret file: %w", err)
+		return settings, fmt.Errorf("reading HTTP proxy user secret file: %w", err)
 	}
 
 	settings.Password, err = readSecretFileAsStringPtr(
@@ -20,7 +20,7 @@ func readHTTPProxy() (settings settings.HTTPProxy, err error) {
 		"/run/secrets/httpproxy_password",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read OpenVPN password secret file: %w", err)
+		return settings, fmt.Errorf("reading OpenVPN password secret file: %w", err)
 	}
 
 	return settings, nil

internal/configuration/sources/secrets/openvpn.go

@@ -13,7 +13,7 @@ func readOpenVPN() (
 		"/run/secrets/openvpn_user",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read user file: %w", err)
+		return settings, fmt.Errorf("reading user file: %w", err)
 	}
 
 	settings.Password, err = readSecretFileAsStringPtr(
@@ -21,7 +21,7 @@ func readOpenVPN() (
 		"/run/secrets/openvpn_password",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read password file: %w", err)
+		return settings, fmt.Errorf("reading password file: %w", err)
 	}
 
 	settings.Key, err = readPEMSecretFile(
@@ -29,7 +29,7 @@ func readOpenVPN() (
 		"/run/secrets/openvpn_clientkey",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read client key file: %w", err)
+		return settings, fmt.Errorf("reading client key file: %w", err)
 	}
 
 	settings.EncryptedKey, err = readPEMSecretFile(
@@ -53,7 +53,7 @@ func readOpenVPN() (
 		"/run/secrets/openvpn_clientcrt",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read client certificate file: %w", err)
+		return settings, fmt.Errorf("reading client certificate file: %w", err)
 	}
 
 	return settings, nil

internal/configuration/sources/secrets/shadowsocks.go

@@ -12,7 +12,7 @@ func readShadowsocks() (settings settings.Shadowsocks, err error) {
 		"/run/secrets/shadowsocks_password",
 	)
 	if err != nil {
-		return settings, fmt.Errorf("cannot read Shadowsocks password secret file: %w", err)
+		return settings, fmt.Errorf("reading Shadowsocks password secret file: %w", err)
 	}
 
 	return settings, nil

internal/configuration/sources/secrets/vpn.go

@@ -9,7 +9,7 @@ import (
 func readVPN() (vpn settings.VPN, err error) {
 	vpn.OpenVPN, err = readOpenVPN()
 	if err != nil {
-		return vpn, fmt.Errorf("cannot read OpenVPN settings: %w", err)
+		return vpn, fmt.Errorf("reading OpenVPN settings: %w", err)
 	}
 
 	return vpn, nil