feat: add client definition and New method.

Author: ghosind

client.go

@@ -0,0 +1,74 @@
+package request
+
+import (
+"net/http"
+"sync"
+"time"
+)
+
+type Client struct {
+// BaseURL will be prepended to all request URL unless URL is absolute.
+BaseURL string
+// Headers are custom headers to be sent.
+Headers http.Header
+// clientPool is for save http.Client instances.
+clientPool sync.Pool
+// timeout specifies the time before the request times out.
+timeout time.Duration
+}
+
+type Config struct {
+// BaseURL will be prepended to all request URL unless URL is absolute.
+BaseURL string
+// Timeout is request timeout in milliseconds.
+Timeout int
+// Headers are custom headers to be sent.
+Headers map[string][]string
+}
+
+var defaultClient *Client
+
+// New creates and returns a new Client instance.
+func New(config ...Config) *Client {
+cli := new(Client)
+
+cli.Headers = make(http.Header)
+cli.clientPool = sync.Pool{
+New: func() any {
+return http.Client{}
+},
+}
+
+if len(config) > 0 {
+cfg := config[0]
+
+cli.BaseURL = cfg.BaseURL
+if cfg.Timeout > 0 {
+cli.SetTimeout(cfg.Timeout)
+}
+cli.setHeader(cfg.Headers)
+}
+
+return cli
+}
+
+// SetTimeout sets client's timeout with a number in milliseconds.
+func (cli *Client) SetTimeout(timeout int) {
+cli.timeout = time.Duration(timeout) * time.Millisecond
+}
+
+// setHeader initializes client's Headers field from config.
+func (cli *Client) setHeader(headers map[string][]string) {
+for k, v := range headers {
+if len(v) > 0 {
+cli.Headers[k] = make([]string, len(v))
+copy(cli.Headers[k], v)
+} else {
+cli.Headers[k] = nil
+}
+}
+}
+
+func init() {
+defaultClient = New()
+}