Started work on resolve package

pkg/resolve/doc.go

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+// Package resolve is used to handle resolving records
+// It also handles wildcard subdomains and rotating resolvers.
+package resolve

pkg/resolve/resolver.go

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+package resolve
+
+import (
+	"bufio"
+	"math/rand"
+	"os"
+	"time"
+)
+
+// DefaultResolvers contains the default list of resolvers known to be good
+var DefaultResolvers = []string{
+	"1.1.1.1",        // Cloudflare primary
+	"1.0.0.1",        // Cloudlfare secondary
+	"8.8.8.8",        // Google primary
+	"8.8.4.4",        // Google secondary
+	"9.9.9.9",        // Quad9 Primary
+	"9.9.9.10",       // Quad9 Secondary
+	"77.88.8.8",      // Yandex Primary
+	"77.88.8.1",      // Yandex Secondary
+	"208.67.222.222", // OpenDNS Primary
+	"208.67.220.220", // OpenDNS Secondary
+}
+
+// Resolver is a struct for resolving DNS names
+type Resolver struct {
+	resolvers []string
+	rand      *rand.Rand
+}
+
+// NewResolver creates a new resolver struct with the default resolvers
+func NewResolver() *Resolver {
+	return &Resolver{
+		resolvers: []string{},
+		rand:      rand.New(rand.NewSource(time.Now().UnixNano())),
+	}
+}
+
+// AppendResolversFromFile appends the resolvers read from a file to the list of resolvers
+func (r *Resolver) AppendResolversFromFile(file string) error {
+	f, err := os.Open(file)
+	if err != nil {
+		return err
+	}
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		text := scanner.Text()
+		if text == "" {
+			continue
+		}
+		r.resolvers = append(r.resolvers, text)
+	}
+	f.Close()
+	return scanner.Err()
+}
+
+// AppendResolversFromSlice appends the slice to the list of resolvers
+func (r *Resolver) AppendResolversFromSlice(list []string) {
+	r.resolvers = append(r.resolvers, list...)
+}