Working with files in Go involves understanding how to effectively write data while managing file modes and permissions. Unlike reading files, writing data can present challenges, particularly regarding whether to append to an existing file or truncate it. The `os.create` function can be convenient but will replace existing content unless specified otherwise. To append data instead, the `os.openFile` function is preferred as it provides more control over file behavior, including flags for read and write permissions and the ability to use `O_APPEND` to add data without losing existing content. Correctly setting permissions, such as `0644`, governs user access to the file and ensures that proper read/write privileges are enforced. Understanding these aspects not only simplifies code management but also enhances data integrity when building CLI applications.