Yet another "static" confusion

[Lubos Pintes]

Hi,
I want to allocate a buffer which I use in a function which reads data 
from socket.
So I did as a first line in that function:
static char[] buffer=new char[4096];

The compiler (2.062) complained that it cannot evaluate new char[] at 
compile time.
I Then tried to move the declaration before function, the same thing 
happened. Allocating statically sized array bloats the executable.
My idea is to return only a slice of array if less than 4K data was read 
and prevent new allocation on every read.

So what I am doing wrong or is this not possible?
Thank.