add num_cpus crate

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "Inflector"
 version = "0.11.4"
@@ -1247,6 +1249,7 @@ dependencies = [
  "lazy_static",
  "log",
  "native-tls",
+ "num_cpus",
  "prettytable-rs",
  "rand 0.7.3",
  "rand_core 0.5.1",

Cargo.toml

@@ -34,6 +34,7 @@ bimap = "0.5.2"
 hex = "0.4.2"
 bs58 = "0.4.0"
 prettytable-rs = "0.8"
+num_cpus = "1.13.0"
 
 smol = "1.2.4"
 futures = "0.3.17"