chore: fix linting errors (#36)

Author: jesusprubio

README.md

@@ -3,7 +3,7 @@
   <img alt="Logo" src="https://media.giphy.com/media/pYyFAHLW0zJL2/giphy.gif" width="40%">
 </div>
 
-Troubleshoot problems with your Internet connection based om different
+Troubleshoot problems with your Internet connection based on different
 [protocols](pkg/protocol.go) and [public servers](pkg/servers.go).
 
 [![GoDoc][doc-img]][doc] [![Build Status][ci-img]][ci] ![License](https://img.shields.io/github/license/jesusprubio/up)

pkg/probe.go

@@ -75,7 +75,10 @@ func (p Probe) Run(ctx context.Context) error {
 					return nil
 				default:
 					start := time.Now()
-					rhost := proto.RHost()
+					rhost, err := proto.RHost()
+					if err != nil {
+						return fmt.Errorf("creating remote host: %w", err)
+					}
 					p.Logger.Debug(
 						"New protocol",
 						"count", count, "protocol", proto.ID, "rhost", rhost,

pkg/protocol.go

@@ -10,7 +10,7 @@ import (
 // Protocols included in the library.
 var Protocols = []*Protocol{
 	{ID: "http", Request: requestHTTP, RHost: RandomCaptivePortal},
-	{ID: "tcp", Request: requestTCP, RHost: RandomServerTCP},
+	{ID: "tcp", Request: requestTCP, RHost: RandomTCPServer},
 	{ID: "dns", Request: requestDNS, RHost: RandomDomain},
 }
 
@@ -31,7 +31,7 @@ type Protocol struct {
 	// Returns extra information about the attempt or an error if it failed.
 	Request func(rhost string, timeout time.Duration) (string, error)
 	// Function to create a random remote
-	RHost func() string
+	RHost func() (string, error)
 }
 
 // String returns an human-readable representation of the protocol.

pkg/servers.go

@@ -1,15 +1,26 @@
 package pkg
 
 import (
-	"math/rand"
+	"crypto/rand"
+	"fmt"
+	"math/big"
 	"net"
 	"net/url"
 )
 
+const tmplRandom = "creating random number: %w"
+
 // RandomCaptivePortal returns a captive portal URL selected randomly from the
 // list of well-known companies.
-func RandomCaptivePortal() string {
-	return CaptivePortals[rand.Intn(len(CaptivePortals))].String()
+//
+// Returns an error if the random number generator fails.
+func RandomCaptivePortal() (string, error) {
+	count := big.NewInt(int64(len(CaptivePortals)))
+	index, err := rand.Int(rand.Reader, count)
+	if err != nil {
+		return "", fmt.Errorf(tmplRandom, err)
+	}
+	return CaptivePortals[index.Int64()].String(), nil
 }
 
 // CaptivePortals are URLs that well-known companies use inspect the network
@@ -57,9 +68,16 @@ var CaptivePortals []*url.URL = []*url.URL{
 	},
 }
 
-// RandomServerDNS returns a randomly selected public DNS server address.
-func RandomServerDNS() string {
-	return Resolvers[rand.Intn(len(Resolvers))].String()
+// RandomDNSServer returns a randomly selected public DNS server address.
+//
+// Returns an error if the random number generator fails.
+func RandomDNSServer() (string, error) {
+	count := big.NewInt(int64(len(Resolvers)))
+	index, err := rand.Int(rand.Reader, count)
+	if err != nil {
+		return "", fmt.Errorf(tmplRandom, err)
+	}
+	return Resolvers[index.Int64()].String(), nil
 }
 
 // Resolvers is a list of public DNS server IP addresses.
@@ -102,15 +120,29 @@ var Resolvers = []*net.IP{
 	{199, 85, 127, 10},
 }
 
-// RandomServerTCP returns a TCP host:port selected randomly from the public DNS
+// RandomTCPServer returns a TCP host:port selected randomly from the public DNS
 // servers.
-func RandomServerTCP() string {
-	return net.JoinHostPort(RandomServerDNS(), "53")
+//
+// Returns an error if the random number generator fails.
+func RandomTCPServer() (string, error) {
+	serverAddr, err := RandomDNSServer()
+	if err != nil {
+		return "", fmt.Errorf(tmplRandom, err)
+	}
+	return net.JoinHostPort(serverAddr, "53"), nil
 }
 
 // RandomDomain returns a domain selected randomly from the captive portals.
-func RandomDomain() string {
-	// Error ignored because the URLs are hardcoded.
-	u, _ := url.Parse(RandomCaptivePortal())
-	return u.Hostname()
+//
+// Returns an error if the random number generator fails.
+func RandomDomain() (string, error) {
+	portalURL, err := RandomCaptivePortal()
+	if err != nil {
+		return "", fmt.Errorf(tmplRandom, err)
+	}
+	u, err := url.Parse(portalURL)
+	if err != nil {
+		return "", fmt.Errorf("parsing URL %s: %w", portalURL, err)
+	}
+	return u.Hostname(), nil
 }