diff --git a/Cargo.lock b/Cargo.lock
index f3527f7..8ffab5e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -71,7 +71,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0df2f85c8a2abbe3b7d7e748052fdd9b76a0458fdeb16ad4223f5eca78c7c130"
 dependencies = [
  "addr2line",
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "object",
  "rustc-demangle",
@@ -128,6 +128,12 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "chrono"
 version = "0.4.11"
@@ -203,7 +209,7 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ba125de2af0df55319f41944744ad91c71113bf74a4646efff39afe1f6842db1"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
 ]
 
 [[package]]
@@ -212,7 +218,7 @@ version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "69323bff1fb41c635347b8ead484a5ca6c3f11914d784170b158d8449ab07f8e"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "crossbeam-channel",
  "crossbeam-deque",
  "crossbeam-epoch",
@@ -248,7 +254,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "058ed274caafc1f60c4997b5fc07bf7dc7cca454af7c6e81edffe5f33f70dace"
 dependencies = [
  "autocfg 1.0.0",
- "cfg-if",
+ "cfg-if 0.1.10",
  "crossbeam-utils",
  "lazy_static",
  "maybe-uninit",
@@ -262,7 +268,7 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c695eeca1e7173472a32221542ae469b3e9aac3a4fc81f7696bcad82029493db"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "crossbeam-utils",
 ]
 
@@ -273,7 +279,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
 dependencies = [
  "autocfg 1.0.0",
- "cfg-if",
+ "cfg-if 0.1.10",
  "lazy_static",
 ]
 
@@ -334,7 +340,7 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "affc17579b132fc2461adf7c575cc6e8b134ebca52c51f5411388965227dc695"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "redox_syscall",
  "winapi 0.3.8",
@@ -351,7 +357,7 @@ dependencies = [
  "log",
  "num_cpus",
  "partial_application",
- "rand 0.7.3",
+ "rand 0.8.2",
  "simple_logger",
  "structopt",
  "tantivy",
@@ -527,9 +533,20 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7abc8dd8451921606d809ba32e95b6111925cd2906060d2dcc29c070220503eb"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
+ "libc",
+ "wasi 0.9.0+wasi-snapshot-preview1",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4060f4657be78b8e766215b02b18a2e862d83745545de804638e2b545e81aee6"
+dependencies = [
+ "cfg-if 1.0.0",
  "libc",
- "wasi",
+ "wasi 0.10.1+wasi-snapshot-preview1",
 ]
 
 [[package]]
@@ -649,7 +666,7 @@ version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "14b6052be84e6b71ab17edffc2eeabf5c2c3ae1fdb464aae35ac50c67a44e1f7"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
 ]
 
 [[package]]
@@ -689,7 +706,7 @@ version = "0.6.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fce347092656428bc8eaf6201042cb551b8d67855af7374542a92a0fbfcac430"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "fuchsia-zircon",
  "fuchsia-zircon-sys",
  "iovec",
@@ -741,7 +758,7 @@ version = "0.2.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2ba7c918ac76704fb42afcbbb43891e72731f3dcca3bef2a19786297baf14af7"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "winapi 0.3.8",
 ]
@@ -754,7 +771,7 @@ checksum = "6c722bee1037d430d0f8e687bbdbf222f27cc6e4e68d5caf630857bb2b6dbdce"
 dependencies = [
  "bitflags",
  "cc",
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "void",
 ]
@@ -968,13 +985,25 @@ version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
 dependencies = [
- "getrandom",
+ "getrandom 0.1.14",
  "libc",
  "rand_chacha 0.2.2",
  "rand_core 0.5.1",
  "rand_hc 0.2.0",
 ]
 
+[[package]]
+name = "rand"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "18519b42a40024d661e1714153e9ad0c3de27cd495760ceb09710920f1098b1e"
+dependencies = [
+ "libc",
+ "rand_chacha 0.3.0",
+ "rand_core 0.6.1",
+ "rand_hc 0.3.0",
+]
+
 [[package]]
 name = "rand_chacha"
 version = "0.1.1"
@@ -995,6 +1024,16 @@ dependencies = [
  "rand_core 0.5.1",
 ]
 
+[[package]]
+name = "rand_chacha"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.6.1",
+]
+
 [[package]]
 name = "rand_core"
 version = "0.3.1"
@@ -1016,7 +1055,16 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
 dependencies = [
- "getrandom",
+ "getrandom 0.1.14",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c026d7df8b298d90ccbbc5190bd04d85e159eaf5576caeacf8741da93ccbd2e5"
+dependencies = [
+ "getrandom 0.2.1",
 ]
 
 [[package]]
@@ -1037,6 +1085,15 @@ dependencies = [
  "rand_core 0.5.1",
 ]
 
+[[package]]
+name = "rand_hc"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73"
+dependencies = [
+ "rand_core 0.6.1",
+]
+
 [[package]]
 name = "rand_isaac"
 version = "0.1.1"
@@ -1416,7 +1473,7 @@ version = "3.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "rand 0.7.3",
  "redox_syscall",
@@ -1530,6 +1587,12 @@ version = "0.9.0+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
 
+[[package]]
+name = "wasi"
+version = "0.10.1+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93c6c3420963c5c64bca373b25e77acb562081b9bb4dd5bb864187742186cea9"
+
 [[package]]
 name = "winapi"
 version = "0.2.8"
diff --git a/Cargo.toml b/Cargo.toml
index f123abf..3bb4358 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,7 +32,7 @@ simple_logger = "1.5.0"
 threadpool = "1.7.1"
 partial_application = "0.2.0"
 num_cpus = "1.12.0"
-rand = "0.7.3"
+rand = "0.8.2"