Add user-agent string

Signed-off-by: Saswata Mukherjee <saswataminsta@yahoo.com>

pkg/mdformatter/linktransformer/validator.go

@@ -86,8 +86,16 @@ func getGitHubRegex(repoRe string) (*regexp.Regexp, int, error) {
 	var pullNum []GitHubResponse
 	var issueNum []GitHubResponse
 	max := 0
+	// All GitHub API reqs need to have User-Agent: https://docs.github.com/en/rest/overview/resources-in-the-rest-api#user-agent-required.
+	client := &http.Client{}
+
 	// Check latest pull request number.
-	respPull, err := http.Get(fmt.Sprintf(gitHubAPIURL, reponame, "pulls"))
+	reqPull, err := http.NewRequest("GET", fmt.Sprintf(gitHubAPIURL, reponame, "pulls"), nil)
+	if err != nil {
+		return nil, math.MaxInt64, err
+	}
+	reqPull.Header.Set("User-Agent", "mdox")
+	respPull, err := client.Do(reqPull)
 	if err != nil {
 		return nil, math.MaxInt64, err
 	}
@@ -103,7 +111,12 @@ func getGitHubRegex(repoRe string) (*regexp.Regexp, int, error) {
 	}
 
 	// Check latest issue number and return whichever is greater.
-	respIssue, err := http.Get(fmt.Sprintf(gitHubAPIURL, reponame, "issues"))
+	reqIssue, err := http.NewRequest("GET", fmt.Sprintf(gitHubAPIURL, reponame, "issues"), nil)
+	if err != nil {
+		return nil, math.MaxInt64, err
+	}
+	reqIssue.Header.Set("User-Agent", "mdox")
+	respIssue, err := client.Do(reqIssue)
 	if err != nil {
 		return nil, math.MaxInt64, err
 	}