Function library_blockchain::lib_block_concat_two_string

pub fn lib_block_concat_two_string(str1: String, str2: String) -> String

In the stable version rust that we used is concat macro.
🔬 For a nightly-only experimental API. (slice_concat_trait #27747) https://doc.rust-lang.org/std/slice/trait.Concat.html# Another Solution
#[macro_use(concat_string)]

extern crate concat_string;
pub fn blockchain_concat_two_str(str:String,num:String)-> String {    
    let output=concat_string!(str,num);    
    output
}