Join lines of two lines

I want to join the lines of two files. So I have file1:

A
B
C
D
E
F

and file 2:

G
H
I
J
K
L

and get:

AG
BH
CI
DJ
EK
FL

Use awk like this (robbed and modified from various places on the internet):

awk '{str = $0 ; getline < "run1717_1731_1.end2.pf.fastq" ; print str $0 > "run1717_1731_1_joined.fastq"}' run1717_1731_1.end1.pf.fastq