Replace futures dependency with futures_util

The latter is sufficient, and the former pulls over a dozen additional
unused dependencies.

Closes: NLnetLabs#245

Cargo.toml

@@ -23,7 +23,7 @@ time           = "0.3.1"
 rand           = { version = "0.8", optional = true }
 bytes          = { version = "1.0", optional = true }
 chrono         = { version = "0.4.6", optional = true, default-features = false }
-futures        = { version = "0.3", optional = true }
+futures-util   = { version = "0.3", optional = true }
 heapless       = { version = "0.7", optional = true }
 #openssl       = { version = "0.10", optional = true }
 ring           = { version = "0.17", optional = true }
@@ -41,7 +41,7 @@ default     = ["std", "rand"]
 bytes       = ["dep:bytes", "octseq/bytes"]
 heapless    = ["dep:heapless", "octseq/heapless"]
 interop     = ["bytes", "ring"]
-resolv      = ["bytes", "futures", "smallvec", "std", "tokio", "libc", "rand"]
+resolv      = ["bytes", "futures-util", "smallvec", "std", "tokio", "libc", "rand"]
 resolv-sync = ["resolv", "tokio/rt"]
 serde       = ["dep:serde", "octseq/serde"]
 sign        = ["std"]

Changelog.md

@@ -10,6 +10,8 @@ Bug fixes
 
 Other changes
 
+* The `resolv` feature now depends on `futures_util` instead of `futures`,
+  trimming unused dependencies from the the dependency tree.
 
 ## 0.9.2
 

src/resolv/lookup/srv.rs

@@ -8,8 +8,7 @@ use crate::base::wire::ParseError;
 use crate::rdata::{Aaaa, Srv, A};
 use crate::resolv::resolver::Resolver;
 use core::fmt;
-use futures::stream;
-use futures::stream::{Stream, StreamExt};
+use futures_util::stream::{self, Stream, StreamExt};
 use octseq::octets::Octets;
 use rand::distributions::{Distribution, Uniform};
 use std::net::{IpAddr, SocketAddr};