If your progression is in the key of A, then the diatonic chords will feature heavily … A, Bm, C#m, E, F#m and the G as a borrowed chord will make fleeting appearances and be notable for the alteration in the overall sound it brings which will cause your ears to prick up a little at something unexpected.
If your progressions is modal in A mixolydian, it will bounce back and forth between A and G a lot, tend to have just a few chords, perhaps Em too (as it contains the b7 note of G). Try playing the A as A7 and the G as Gmaj7. If that fits the vibe and sound then you’re surely playing Mixolydian.
This progressions with a borrowed bVII is in Ab with the Gb borrowed so half a step down from yours, the logic applies the same though - Using borrowed chords - introduction + examples
Mixolydian: Modes Parts 1 - 7 - #108 by Richard_close2u