docs: add GOPATH/bin PATH hint for go install

Author: debidong

README.md

@@ -24,6 +24,11 @@ irm https://raw.githubusercontent.com/flashcatcloud/flashduty-cli/main/install.p
 go install github.com/flashcatcloud/flashduty-cli/cmd/flashduty@latest
 ```
 
+> Make sure `$(go env GOPATH)/bin` is in your `PATH`. If `flashduty` is not found after install, run:
+> ```bash
+> export PATH="$(go env GOPATH)/bin:$PATH"
+> ```
+
 ### Manual Download
 
 Download the latest release for your platform from [GitHub Releases](https://github.com/flashcatcloud/flashduty-cli/releases).

README_zh.md

@@ -24,6 +24,11 @@ irm https://raw.githubusercontent.com/flashcatcloud/flashduty-cli/main/install.p
 go install github.com/flashcatcloud/flashduty-cli/cmd/flashduty@latest
 ```
 
+> 确保 `$(go env GOPATH)/bin` 在您的 `PATH` 中。如果安装后找不到 `flashduty`，请运行：
+> ```bash
+> export PATH="$(go env GOPATH)/bin:$PATH"
+> ```
+
 ### 手动下载
 
 从 [GitHub Releases](https://github.com/flashcatcloud/flashduty-cli/releases) 下载适合您平台的最新版本。