Go to beginning of line without opening new line in VI

You can use ^ or 0 (Zero) in normal mode to move to the beginning of a line.

^ moves the cursor to the first non-blank character of a line
0 always moves the cursor to the "first column"

You can also use Shifti to move and switch to Insert mode.

A simple 0 takes you to the beginning of a line.

:help 0 for more information

Try this Vi/Vim cheatsheet solution to many problems.

For normal mode :
0 - [zero] to beginning of line, first column.
$ - to end of line