Intro/Outro/Verse: F#m  F#m  D  C#m . I couldn't tab the exact base line, but I 
tried to make similar one, here it is:

E|2-2--------------------| 2-2---------------5-7-|
B|-----4---4-5-5--5-4-4--|-----4---4-5-7-5-4----|
G|------4----------------|------4---------------|
D|-----------------------|----------------------|
A|-----------------------|----------------------|
E|-----------------------|----------------------|

   Verse:

   F#m   F#m    D    C#
Summer came to an end,
   F#m   F#m    D    C#
We're saying good bye to friends,
   F#m   F#m    D    C#
We met this month,
We'll keep in touch,
   F#m   F#m    D    C#
I wish time would stop instead.

   F#m   F#m    D    C#
'Cause I don't wanna say good bye,
   F#m   F#m    D    C#
When I'm caught up in your eyes.
   F#m   F#m    D    C#
I wanna stay like this,
Like our first kiss,
   F#m   F#m    D    C#           
That brought my heart to life.
   
   F#m E before the chorus

 Chorus:
 A     D   A
Don't let go,
 E               A     D   A
Tell her so she won't let go.
 E
She may never know.
 A
So tell her,
 D
I should tell her,
 A                 E
Before my heart explodes.
 A     D   A
Don't let go,
 E                 
I won't let you go. 

 F#m  F#m  D  C#m x2

 F#m  F#m    D    C#m
The nights are getting cold,
 F#m  F#m    D    C#m
And the days are hard to hold.
 F#m  F#m    D    C#m
You're months away and miles from me,
 F#m  F#m    D    C#m
But the memory's still gold.
 F#m  F#m    D    C#m
I think about them all the time,
 F#m  F#m    D    C#m
That summer when you were mine.
 F#m  F#m    D    C#m
Before I caved in, my words felt thin,
 F#m  F#m    D    C#m     F#m   E   
Don't wanna say good bye, goodbye.

 A     D   A
Don't let go,
 E               A     D   A
Tell her so she won't let go.
 E
She may never know.
 A
So tell her,
 D
I should tell her,
 A                 E
Before my heart explodes.
 A     D   A
Don't let go,
 E                 
I won't let you go. 

 Bridge:

D      A               E
Please take me back to summer,
   F#m   E        D
So I can let you know,
D    A                  E
This year's been such a bummer,
   F#m   E        D
Because I let you go.
D      A               E
Please take me back to summer,
   F#m   E        D
So I can let you know,
D    A                  E
This year's been such a bummer,
   F#m   E          A   D   A   E  x2
Because I let you go.